17 files changed, 409 insertions, 646 deletions
diff --git a/vendor/golang.org/x/tools/AUTHORS b/vendor/golang.org/x/tools/AUTHORS
new file mode 100644
index 000000000..15167cd74
--- /dev/null
+++ b/vendor/golang.org/x/tools/AUTHORS
@@ -0,0 +1,3 @@
+# This source code refers to The Go Authors for copyright purposes.
+# The master list of authors is in the main Go distribution,
+# visible at http://tip.golang.org/AUTHORS.
diff --git a/vendor/golang.org/x/tools/CONTRIBUTORS b/vendor/golang.org/x/tools/CONTRIBUTORS
new file mode 100644
index 000000000..1c4577e96
--- /dev/null
+++ b/vendor/golang.org/x/tools/CONTRIBUTORS
@@ -0,0 +1,3 @@
+# This source code was written by the Go contributors.
+# The master list of contributors is in the main Go distribution,
+# visible at http://tip.golang.org/CONTRIBUTORS.
diff --git a/vendor/golang.org/x/xerrors/LICENSE b/vendor/golang.org/x/tools/LICENSE
index e4a47e17f..6a66aea5e 100644
--- a/vendor/golang.org/x/xerrors/LICENSE
+++ b/vendor/golang.org/x/tools/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2019 The Go Authors. All rights reserved.
+Copyright (c) 2009 The Go Authors. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
diff --git a/vendor/golang.org/x/xerrors/PATENTS b/vendor/golang.org/x/tools/PATENTS
index 733099041..733099041 100644
--- a/vendor/golang.org/x/xerrors/PATENTS
+++ b/vendor/golang.org/x/tools/PATENTS
diff --git a/vendor/golang.org/x/tools/go/ast/inspector/inspector.go b/vendor/golang.org/x/tools/go/ast/inspector/inspector.go
new file mode 100644
index 000000000..af5e17fee
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ast/inspector/inspector.go
@@ -0,0 +1,186 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package inspector provides helper functions for traversal over the
+// syntax trees of a package, including node filtering by type, and
+// materialization of the traversal stack.
+//
+// During construction, the inspector does a complete traversal and
+// builds a list of push/pop events and their node type. Subsequent
+// method calls that request a traversal scan this list, rather than walk
+// the AST, and perform type filtering using efficient bit sets.
+//
+// Experiments suggest the inspector's traversals are about 2.5x faster
+// than ast.Inspect, but it may take around 5 traversals for this
+// benefit to amortize the inspector's construction cost.
+// If efficiency is the primary concern, do not use Inspector for
+// one-off traversals.
+package inspector
+
+// There are four orthogonal features in a traversal:
+//  1 type filtering
+//  2 pruning
+//  3 postorder calls to f
+//  4 stack
+// Rather than offer all of them in the API,
+// only a few combinations are exposed:
+// - Preorder is the fastest and has fewest features,
+//   but is the most commonly needed traversal.
+// - Nodes and WithStack both provide pruning and postorder calls,
+//   even though few clients need it, because supporting two versions
+//   is not justified.
+// More combinations could be supported by expressing them as
+// wrappers around a more generic traversal, but this was measured
+// and found to degrade performance significantly (30%).
+
+import (
+	"go/ast"
+)
+
+// An Inspector provides methods for inspecting
+// (traversing) the syntax trees of a package.
+type Inspector struct {
+	events []event
+}
+
+// New returns an Inspector for the specified syntax trees.
+func New(files []*ast.File) *Inspector {
+	return &Inspector{traverse(files)}
+}
+
+// An event represents a push or a pop
+// of an ast.Node during a traversal.
+type event struct {
+	node  ast.Node
+	typ   uint64 // typeOf(node)
+	index int    // 1 + index of corresponding pop event, or 0 if this is a pop
+}
+
+// Preorder visits all the nodes of the files supplied to New in
+// depth-first order. It calls f(n) for each node n before it visits
+// n's children.
+//
+// The types argument, if non-empty, enables type-based filtering of
+// events. The function f if is called only for nodes whose type
+// matches an element of the types slice.
+func (in *Inspector) Preorder(types []ast.Node, f func(ast.Node)) {
+	// Because it avoids postorder calls to f, and the pruning
+	// check, Preorder is almost twice as fast as Nodes. The two
+	// features seem to contribute similar slowdowns (~1.4x each).
+
+	mask := maskOf(types)
+	for i := 0; i < len(in.events); {
+		ev := in.events[i]
+		if ev.typ&mask != 0 {
+			if ev.index > 0 {
+				f(ev.node)
+			}
+		}
+		i++
+	}
+}
+
+// Nodes visits the nodes of the files supplied to New in depth-first
+// order. It calls f(n, true) for each node n before it visits n's
+// children. If f returns true, Nodes invokes f recursively for each
+// of the non-nil children of the node, followed by a call of
+// f(n, false).
+//
+// The types argument, if non-empty, enables type-based filtering of
+// events. The function f if is called only for nodes whose type
+// matches an element of the types slice.
+func (in *Inspector) Nodes(types []ast.Node, f func(n ast.Node, push bool) (proceed bool)) {
+	mask := maskOf(types)
+	for i := 0; i < len(in.events); {
+		ev := in.events[i]
+		if ev.typ&mask != 0 {
+			if ev.index > 0 {
+				// push
+				if !f(ev.node, true) {
+					i = ev.index // jump to corresponding pop + 1
+					continue
+				}
+			} else {
+				// pop
+				f(ev.node, false)
+			}
+		}
+		i++
+	}
+}
+
+// WithStack visits nodes in a similar manner to Nodes, but it
+// supplies each call to f an additional argument, the current
+// traversal stack. The stack's first element is the outermost node,
+// an *ast.File; its last is the innermost, n.
+func (in *Inspector) WithStack(types []ast.Node, f func(n ast.Node, push bool, stack []ast.Node) (proceed bool)) {
+	mask := maskOf(types)
+	var stack []ast.Node
+	for i := 0; i < len(in.events); {
+		ev := in.events[i]
+		if ev.index > 0 {
+			// push
+			stack = append(stack, ev.node)
+			if ev.typ&mask != 0 {
+				if !f(ev.node, true, stack) {
+					i = ev.index
+					stack = stack[:len(stack)-1]
+					continue
+				}
+			}
+		} else {
+			// pop
+			if ev.typ&mask != 0 {
+				f(ev.node, false, stack)
+			}
+			stack = stack[:len(stack)-1]
+		}
+		i++
+	}
+}
+
+// traverse builds the table of events representing a traversal.
+func traverse(files []*ast.File) []event {
+	// Preallocate approximate number of events
+	// based on source file extent.
+	// This makes traverse faster by 4x (!).
+	var extent int
+	for _, f := range files {
+		extent += int(f.End() - f.Pos())
+	}
+	// This estimate is based on the net/http package.
+	capacity := extent * 33 / 100
+	if capacity > 1e6 {
+		capacity = 1e6 // impose some reasonable maximum
+	}
+	events := make([]event, 0, capacity)
+
+	var stack []event
+	for _, f := range files {
+		ast.Inspect(f, func(n ast.Node) bool {
+			if n != nil {
+				// push
+				ev := event{
+					node:  n,
+					typ:   typeOf(n),
+					index: len(events), // push event temporarily holds own index
+				}
+				stack = append(stack, ev)
+				events = append(events, ev)
+			} else {
+				// pop
+				ev := stack[len(stack)-1]
+				stack = stack[:len(stack)-1]
+
+				events[ev.index].index = len(events) + 1 // make push refer to pop
+
+				ev.index = 0 // turn ev into a pop event
+				events = append(events, ev)
+			}
+			return true
+		})
+	}
+
+	return events
+}
diff --git a/vendor/golang.org/x/tools/go/ast/inspector/typeof.go b/vendor/golang.org/x/tools/go/ast/inspector/typeof.go
new file mode 100644
index 000000000..d61301b13
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ast/inspector/typeof.go
@@ -0,0 +1,216 @@
+package inspector
+
+// This file defines func typeOf(ast.Node) uint64.
+//
+// The initial map-based implementation was too slow;
+// see https://go-review.googlesource.com/c/tools/+/135655/1/go/ast/inspector/inspector.go#196
+
+import "go/ast"
+
+const (
+	nArrayType = iota
+	nAssignStmt
+	nBadDecl
+	nBadExpr
+	nBadStmt
+	nBasicLit
+	nBinaryExpr
+	nBlockStmt
+	nBranchStmt
+	nCallExpr
+	nCaseClause
+	nChanType
+	nCommClause
+	nComment
+	nCommentGroup
+	nCompositeLit
+	nDeclStmt
+	nDeferStmt
+	nEllipsis
+	nEmptyStmt
+	nExprStmt
+	nField
+	nFieldList
+	nFile
+	nForStmt
+	nFuncDecl
+	nFuncLit
+	nFuncType
+	nGenDecl
+	nGoStmt
+	nIdent
+	nIfStmt
+	nImportSpec
+	nIncDecStmt
+	nIndexExpr
+	nInterfaceType
+	nKeyValueExpr
+	nLabeledStmt
+	nMapType
+	nPackage
+	nParenExpr
+	nRangeStmt
+	nReturnStmt
+	nSelectStmt
+	nSelectorExpr
+	nSendStmt
+	nSliceExpr
+	nStarExpr
+	nStructType
+	nSwitchStmt
+	nTypeAssertExpr
+	nTypeSpec
+	nTypeSwitchStmt
+	nUnaryExpr
+	nValueSpec
+)
+
+// typeOf returns a distinct single-bit value that represents the type of n.
+//
+// Various implementations were benchmarked with BenchmarkNewInspector:
+//								GOGC=off
+// - type switch				4.9-5.5ms	2.1ms
+// - binary search over a sorted list of types  5.5-5.9ms	2.5ms
+// - linear scan, frequency-ordered list 	5.9-6.1ms	2.7ms
+// - linear scan, unordered list		6.4ms		2.7ms
+// - hash table					6.5ms		3.1ms
+// A perfect hash seemed like overkill.
+//
+// The compiler's switch statement is the clear winner
+// as it produces a binary tree in code,
+// with constant conditions and good branch prediction.
+// (Sadly it is the most verbose in source code.)
+// Binary search suffered from poor branch prediction.
+//
+func typeOf(n ast.Node) uint64 {
+	// Fast path: nearly half of all nodes are identifiers.
+	if _, ok := n.(*ast.Ident); ok {
+		return 1 << nIdent
+	}
+
+	// These cases include all nodes encountered by ast.Inspect.
+	switch n.(type) {
+	case *ast.ArrayType:
+		return 1 << nArrayType
+	case *ast.AssignStmt:
+		return 1 << nAssignStmt
+	case *ast.BadDecl:
+		return 1 << nBadDecl
+	case *ast.BadExpr:
+		return 1 << nBadExpr
+	case *ast.BadStmt:
+		return 1 << nBadStmt
+	case *ast.BasicLit:
+		return 1 << nBasicLit
+	case *ast.BinaryExpr:
+		return 1 << nBinaryExpr
+	case *ast.BlockStmt:
+		return 1 << nBlockStmt
+	case *ast.BranchStmt:
+		return 1 << nBranchStmt
+	case *ast.CallExpr:
+		return 1 << nCallExpr
+	case *ast.CaseClause:
+		return 1 << nCaseClause
+	case *ast.ChanType:
+		return 1 << nChanType
+	case *ast.CommClause:
+		return 1 << nCommClause
+	case *ast.Comment:
+		return 1 << nComment
+	case *ast.CommentGroup:
+		return 1 << nCommentGroup
+	case *ast.CompositeLit:
+		return 1 << nCompositeLit
+	case *ast.DeclStmt:
+		return 1 << nDeclStmt
+	case *ast.DeferStmt:
+		return 1 << nDeferStmt
+	case *ast.Ellipsis:
+		return 1 << nEllipsis
+	case *ast.EmptyStmt:
+		return 1 << nEmptyStmt
+	case *ast.ExprStmt:
+		return 1 << nExprStmt
+	case *ast.Field:
+		return 1 << nField
+	case *ast.FieldList:
+		return 1 << nFieldList
+	case *ast.File:
+		return 1 << nFile
+	case *ast.ForStmt:
+		return 1 << nForStmt
+	case *ast.FuncDecl:
+		return 1 << nFuncDecl
+	case *ast.FuncLit:
+		return 1 << nFuncLit
+	case *ast.FuncType:
+		return 1 << nFuncType
+	case *ast.GenDecl:
+		return 1 << nGenDecl
+	case *ast.GoStmt:
+		return 1 << nGoStmt
+	case *ast.Ident:
+		return 1 << nIdent
+	case *ast.IfStmt:
+		return 1 << nIfStmt
+	case *ast.ImportSpec:
+		return 1 << nImportSpec
+	case *ast.IncDecStmt:
+		return 1 << nIncDecStmt
+	case *ast.IndexExpr:
+		return 1 << nIndexExpr
+	case *ast.InterfaceType:
+		return 1 << nInterfaceType
+	case *ast.KeyValueExpr:
+		return 1 << nKeyValueExpr
+	case *ast.LabeledStmt:
+		return 1 << nLabeledStmt
+	case *ast.MapType:
+		return 1 << nMapType
+	case *ast.Package:
+		return 1 << nPackage
+	case *ast.ParenExpr:
+		return 1 << nParenExpr
+	case *ast.RangeStmt:
+		return 1 << nRangeStmt
+	case *ast.ReturnStmt:
+		return 1 << nReturnStmt
+	case *ast.SelectStmt:
+		return 1 << nSelectStmt
+	case *ast.SelectorExpr:
+		return 1 << nSelectorExpr
+	case *ast.SendStmt:
+		return 1 << nSendStmt
+	case *ast.SliceExpr:
+		return 1 << nSliceExpr
+	case *ast.StarExpr:
+		return 1 << nStarExpr
+	case *ast.StructType:
+		return 1 << nStructType
+	case *ast.SwitchStmt:
+		return 1 << nSwitchStmt
+	case *ast.TypeAssertExpr:
+		return 1 << nTypeAssertExpr
+	case *ast.TypeSpec:
+		return 1 << nTypeSpec
+	case *ast.TypeSwitchStmt:
+		return 1 << nTypeSwitchStmt
+	case *ast.UnaryExpr:
+		return 1 << nUnaryExpr
+	case *ast.ValueSpec:
+		return 1 << nValueSpec
+	}
+	return 0
+}
+
+func maskOf(nodes []ast.Node) uint64 {
+	if nodes == nil {
+		return 1<<64 - 1 // match all node types
+	}
+	var mask uint64
+	for _, n := range nodes {
+		mask |= typeOf(n)
+	}
+	return mask
+}
diff --git a/vendor/golang.org/x/xerrors/README b/vendor/golang.org/x/xerrors/README
deleted file mode 100644
index aac7867a5..000000000
--- a/vendor/golang.org/x/xerrors/README
+++ /dev/null
@@ -1,2 +0,0 @@
-This repository holds the transition packages for the new Go 1.13 error values.
-See golang.org/design/29934-error-values.
diff --git a/vendor/golang.org/x/xerrors/adaptor.go b/vendor/golang.org/x/xerrors/adaptor.go
deleted file mode 100644
index 4317f2483..000000000
--- a/vendor/golang.org/x/xerrors/adaptor.go
+++ /dev/null
@@ -1,193 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package xerrors
-
-import (
-	"bytes"
-	"fmt"
-	"io"
-	"reflect"
-	"strconv"
-)
-
-// FormatError calls the FormatError method of f with an errors.Printer
-// configured according to s and verb, and writes the result to s.
-func FormatError(f Formatter, s fmt.State, verb rune) {
-	// Assuming this function is only called from the Format method, and given
-	// that FormatError takes precedence over Format, it cannot be called from
-	// any package that supports errors.Formatter. It is therefore safe to
-	// disregard that State may be a specific printer implementation and use one
-	// of our choice instead.
-
-	// limitations: does not support printing error as Go struct.
-
-	var (
-		sep    = " " // separator before next error
-		p      = &state{State: s}
-		direct = true
-	)
-
-	var err error = f
-
-	switch verb {
-	// Note that this switch must match the preference order
-	// for ordinary string printing (%#v before %+v, and so on).
-
-	case 'v':
-		if s.Flag('#') {
-			if stringer, ok := err.(fmt.GoStringer); ok {
-				io.WriteString(&p.buf, stringer.GoString())
-				goto exit
-			}
-			// proceed as if it were %v
-		} else if s.Flag('+') {
-			p.printDetail = true
-			sep = "\n  - "
-		}
-	case 's':
-	case 'q', 'x', 'X':
-		// Use an intermediate buffer in the rare cases that precision,
-		// truncation, or one of the alternative verbs (q, x, and X) are
-		// specified.
-		direct = false
-
-	default:
-		p.buf.WriteString("%!")
-		p.buf.WriteRune(verb)
-		p.buf.WriteByte('(')
-		switch {
-		case err != nil:
-			p.buf.WriteString(reflect.TypeOf(f).String())
-		default:
-			p.buf.WriteString("<nil>")
-		}
-		p.buf.WriteByte(')')
-		io.Copy(s, &p.buf)
-		return
-	}
-
-loop:
-	for {
-		switch v := err.(type) {
-		case Formatter:
-			err = v.FormatError((*printer)(p))
-		case fmt.Formatter:
-			v.Format(p, 'v')
-			break loop
-		default:
-			io.WriteString(&p.buf, v.Error())
-			break loop
-		}
-		if err == nil {
-			break
-		}
-		if p.needColon || !p.printDetail {
-			p.buf.WriteByte(':')
-			p.needColon = false
-		}
-		p.buf.WriteString(sep)
-		p.inDetail = false
-		p.needNewline = false
-	}
-
-exit:
-	width, okW := s.Width()
-	prec, okP := s.Precision()
-
-	if !direct || (okW && width > 0) || okP {
-		// Construct format string from State s.
-		format := []byte{'%'}
-		if s.Flag('-') {
-			format = append(format, '-')
-		}
-		if s.Flag('+') {
-			format = append(format, '+')
-		}
-		if s.Flag(' ') {
-			format = append(format, ' ')
-		}
-		if okW {
-			format = strconv.AppendInt(format, int64(width), 10)
-		}
-		if okP {
-			format = append(format, '.')
-			format = strconv.AppendInt(format, int64(prec), 10)
-		}
-		format = append(format, string(verb)...)
-		fmt.Fprintf(s, string(format), p.buf.String())
-	} else {
-		io.Copy(s, &p.buf)
-	}
-}
-
-var detailSep = []byte("\n    ")
-
-// state tracks error printing state. It implements fmt.State.
-type state struct {
-	fmt.State
-	buf bytes.Buffer
-
-	printDetail bool
-	inDetail    bool
-	needColon   bool
-	needNewline bool
-}
-
-func (s *state) Write(b []byte) (n int, err error) {
-	if s.printDetail {
-		if len(b) == 0 {
-			return 0, nil
-		}
-		if s.inDetail && s.needColon {
-			s.needNewline = true
-			if b[0] == '\n' {
-				b = b[1:]
-			}
-		}
-		k := 0
-		for i, c := range b {
-			if s.needNewline {
-				if s.inDetail && s.needColon {
-					s.buf.WriteByte(':')
-					s.needColon = false
-				}
-				s.buf.Write(detailSep)
-				s.needNewline = false
-			}
-			if c == '\n' {
-				s.buf.Write(b[k:i])
-				k = i + 1
-				s.needNewline = true
-			}
-		}
-		s.buf.Write(b[k:])
-		if !s.inDetail {
-			s.needColon = true
-		}
-	} else if !s.inDetail {
-		s.buf.Write(b)
-	}
-	return len(b), nil
-}
-
-// printer wraps a state to implement an xerrors.Printer.
-type printer state
-
-func (s *printer) Print(args ...interface{}) {
-	if !s.inDetail || s.printDetail {
-		fmt.Fprint((*state)(s), args...)
-	}
-}
-
-func (s *printer) Printf(format string, args ...interface{}) {
-	if !s.inDetail || s.printDetail {
-		fmt.Fprintf((*state)(s), format, args...)
-	}
-}
-
-func (s *printer) Detail() bool {
-	s.inDetail = true
-	return s.printDetail
-}
diff --git a/vendor/golang.org/x/xerrors/codereview.cfg b/vendor/golang.org/x/xerrors/codereview.cfg
deleted file mode 100644
index 3f8b14b64..000000000
--- a/vendor/golang.org/x/xerrors/codereview.cfg
+++ /dev/null
@@ -1 +0,0 @@
-issuerepo: golang/go
diff --git a/vendor/golang.org/x/xerrors/doc.go b/vendor/golang.org/x/xerrors/doc.go
deleted file mode 100644
index eef99d9d5..000000000
--- a/vendor/golang.org/x/xerrors/doc.go
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package xerrors implements functions to manipulate errors.
-//
-// This package is based on the Go 2 proposal for error values:
-//   https://golang.org/design/29934-error-values
-//
-// These functions were incorporated into the standard library's errors package
-// in Go 1.13:
-// - Is
-// - As
-// - Unwrap
-//
-// Also, Errorf's %w verb was incorporated into fmt.Errorf.
-//
-// Use this package to get equivalent behavior in all supported Go versions.
-//
-// No other features of this package were included in Go 1.13, and at present
-// there are no plans to include any of them.
-package xerrors // import "golang.org/x/xerrors"
diff --git a/vendor/golang.org/x/xerrors/errors.go b/vendor/golang.org/x/xerrors/errors.go
deleted file mode 100644
index e88d3772d..000000000
--- a/vendor/golang.org/x/xerrors/errors.go
+++ /dev/null
@@ -1,33 +0,0 @@
-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package xerrors
-
-import "fmt"
-
-// errorString is a trivial implementation of error.
-type errorString struct {
-	s     string
-	frame Frame
-}
-
-// New returns an error that formats as the given text.
-//
-// The returned error contains a Frame set to the caller's location and
-// implements Formatter to show this information when printed with details.
-func New(text string) error {
-	return &errorString{text, Caller(1)}
-}
-
-func (e *errorString) Error() string {
-	return e.s
-}
-
-func (e *errorString) Format(s fmt.State, v rune) { FormatError(e, s, v) }
-
-func (e *errorString) FormatError(p Printer) (next error) {
-	p.Print(e.s)
-	e.frame.Format(p)
-	return nil
-}
diff --git a/vendor/golang.org/x/xerrors/fmt.go b/vendor/golang.org/x/xerrors/fmt.go
deleted file mode 100644
index 829862ddf..000000000
--- a/vendor/golang.org/x/xerrors/fmt.go
+++ /dev/null
@@ -1,187 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package xerrors
-
-import (
-	"fmt"
-	"strings"
-	"unicode"
-	"unicode/utf8"
-
-	"golang.org/x/xerrors/internal"
-)
-
-const percentBangString = "%!"
-
-// Errorf formats according to a format specifier and returns the string as a
-// value that satisfies error.
-//
-// The returned error includes the file and line number of the caller when
-// formatted with additional detail enabled. If the last argument is an error
-// the returned error's Format method will return it if the format string ends
-// with ": %s", ": %v", or ": %w". If the last argument is an error and the
-// format string ends with ": %w", the returned error implements an Unwrap
-// method returning it.
-//
-// If the format specifier includes a %w verb with an error operand in a
-// position other than at the end, the returned error will still implement an
-// Unwrap method returning the operand, but the error's Format method will not
-// return the wrapped error.
-//
-// It is invalid to include more than one %w verb or to supply it with an
-// operand that does not implement the error interface. The %w verb is otherwise
-// a synonym for %v.
-func Errorf(format string, a ...interface{}) error {
-	format = formatPlusW(format)
-	// Support a ": %[wsv]" suffix, which works well with xerrors.Formatter.
-	wrap := strings.HasSuffix(format, ": %w")
-	idx, format2, ok := parsePercentW(format)
-	percentWElsewhere := !wrap && idx >= 0
-	if !percentWElsewhere && (wrap || strings.HasSuffix(format, ": %s") || strings.HasSuffix(format, ": %v")) {
-		err := errorAt(a, len(a)-1)
-		if err == nil {
-			return &noWrapError{fmt.Sprintf(format, a...), nil, Caller(1)}
-		}
-		// TODO: this is not entirely correct. The error value could be
-		// printed elsewhere in format if it mixes numbered with unnumbered
-		// substitutions. With relatively small changes to doPrintf we can
-		// have it optionally ignore extra arguments and pass the argument
-		// list in its entirety.
-		msg := fmt.Sprintf(format[:len(format)-len(": %s")], a[:len(a)-1]...)
-		frame := Frame{}
-		if internal.EnableTrace {
-			frame = Caller(1)
-		}
-		if wrap {
-			return &wrapError{msg, err, frame}
-		}
-		return &noWrapError{msg, err, frame}
-	}
-	// Support %w anywhere.
-	// TODO: don't repeat the wrapped error's message when %w occurs in the middle.
-	msg := fmt.Sprintf(format2, a...)
-	if idx < 0 {
-		return &noWrapError{msg, nil, Caller(1)}
-	}
-	err := errorAt(a, idx)
-	if !ok || err == nil {
-		// Too many %ws or argument of %w is not an error. Approximate the Go
-		// 1.13 fmt.Errorf message.
-		return &noWrapError{fmt.Sprintf("%sw(%s)", percentBangString, msg), nil, Caller(1)}
-	}
-	frame := Frame{}
-	if internal.EnableTrace {
-		frame = Caller(1)
-	}
-	return &wrapError{msg, err, frame}
-}
-
-func errorAt(args []interface{}, i int) error {
-	if i < 0 || i >= len(args) {
-		return nil
-	}
-	err, ok := args[i].(error)
-	if !ok {
-		return nil
-	}
-	return err
-}
-
-// formatPlusW is used to avoid the vet check that will barf at %w.
-func formatPlusW(s string) string {
-	return s
-}
-
-// Return the index of the only %w in format, or -1 if none.
-// Also return a rewritten format string with %w replaced by %v, and
-// false if there is more than one %w.
-// TODO: handle "%[N]w".
-func parsePercentW(format string) (idx int, newFormat string, ok bool) {
-	// Loosely copied from golang.org/x/tools/go/analysis/passes/printf/printf.go.
-	idx = -1
-	ok = true
-	n := 0
-	sz := 0
-	var isW bool
-	for i := 0; i < len(format); i += sz {
-		if format[i] != '%' {
-			sz = 1
-			continue
-		}
-		// "%%" is not a format directive.
-		if i+1 < len(format) && format[i+1] == '%' {
-			sz = 2
-			continue
-		}
-		sz, isW = parsePrintfVerb(format[i:])
-		if isW {
-			if idx >= 0 {
-				ok = false
-			} else {
-				idx = n
-			}
-			// "Replace" the last character, the 'w', with a 'v'.
-			p := i + sz - 1
-			format = format[:p] + "v" + format[p+1:]
-		}
-		n++
-	}
-	return idx, format, ok
-}
-
-// Parse the printf verb starting with a % at s[0].
-// Return how many bytes it occupies and whether the verb is 'w'.
-func parsePrintfVerb(s string) (int, bool) {
-	// Assume only that the directive is a sequence of non-letters followed by a single letter.
-	sz := 0
-	var r rune
-	for i := 1; i < len(s); i += sz {
-		r, sz = utf8.DecodeRuneInString(s[i:])
-		if unicode.IsLetter(r) {
-			return i + sz, r == 'w'
-		}
-	}
-	return len(s), false
-}
-
-type noWrapError struct {
-	msg   string
-	err   error
-	frame Frame
-}
-
-func (e *noWrapError) Error() string {
-	return fmt.Sprint(e)
-}
-
-func (e *noWrapError) Format(s fmt.State, v rune) { FormatError(e, s, v) }
-
-func (e *noWrapError) FormatError(p Printer) (next error) {
-	p.Print(e.msg)
-	e.frame.Format(p)
-	return e.err
-}
-
-type wrapError struct {
-	msg   string
-	err   error
-	frame Frame
-}
-
-func (e *wrapError) Error() string {
-	return fmt.Sprint(e)
-}
-
-func (e *wrapError) Format(s fmt.State, v rune) { FormatError(e, s, v) }
-
-func (e *wrapError) FormatError(p Printer) (next error) {
-	p.Print(e.msg)
-	e.frame.Format(p)
-	return e.err
-}
-
-func (e *wrapError) Unwrap() error {
-	return e.err
-}
diff --git a/vendor/golang.org/x/xerrors/format.go b/vendor/golang.org/x/xerrors/format.go
deleted file mode 100644
index 1bc9c26b9..000000000
--- a/vendor/golang.org/x/xerrors/format.go
+++ /dev/null
@@ -1,34 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package xerrors
-
-// A Formatter formats error messages.
-type Formatter interface {
-	error
-
-	// FormatError prints the receiver's first error and returns the next error in
-	// the error chain, if any.
-	FormatError(p Printer) (next error)
-}
-
-// A Printer formats error messages.
-//
-// The most common implementation of Printer is the one provided by package fmt
-// during Printf (as of Go 1.13). Localization packages such as golang.org/x/text/message
-// typically provide their own implementations.
-type Printer interface {
-	// Print appends args to the message output.
-	Print(args ...interface{})
-
-	// Printf writes a formatted string.
-	Printf(format string, args ...interface{})
-
-	// Detail reports whether error detail is requested.
-	// After the first call to Detail, all text written to the Printer
-	// is formatted as additional detail, or ignored when
-	// detail has not been requested.
-	// If Detail returns false, the caller can avoid printing the detail at all.
-	Detail() bool
-}
diff --git a/vendor/golang.org/x/xerrors/frame.go b/vendor/golang.org/x/xerrors/frame.go
deleted file mode 100644
index 0de628ec5..000000000
--- a/vendor/golang.org/x/xerrors/frame.go
+++ /dev/null
@@ -1,56 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package xerrors
-
-import (
-	"runtime"
-)
-
-// A Frame contains part of a call stack.
-type Frame struct {
-	// Make room for three PCs: the one we were asked for, what it called,
-	// and possibly a PC for skipPleaseUseCallersFrames. See:
-	// https://go.googlesource.com/go/+/032678e0fb/src/runtime/extern.go#169
-	frames [3]uintptr
-}
-
-// Caller returns a Frame that describes a frame on the caller's stack.
-// The argument skip is the number of frames to skip over.
-// Caller(0) returns the frame for the caller of Caller.
-func Caller(skip int) Frame {
-	var s Frame
-	runtime.Callers(skip+1, s.frames[:])
-	return s
-}
-
-// location reports the file, line, and function of a frame.
-//
-// The returned function may be "" even if file and line are not.
-func (f Frame) location() (function, file string, line int) {
-	frames := runtime.CallersFrames(f.frames[:])
-	if _, ok := frames.Next(); !ok {
-		return "", "", 0
-	}
-	fr, ok := frames.Next()
-	if !ok {
-		return "", "", 0
-	}
-	return fr.Function, fr.File, fr.Line
-}
-
-// Format prints the stack as error detail.
-// It should be called from an error's Format implementation
-// after printing any other error detail.
-func (f Frame) Format(p Printer) {
-	if p.Detail() {
-		function, file, line := f.location()
-		if function != "" {
-			p.Printf("%s\n    ", function)
-		}
-		if file != "" {
-			p.Printf("%s:%d\n", file, line)
-		}
-	}
-}
diff --git a/vendor/golang.org/x/xerrors/go.mod b/vendor/golang.org/x/xerrors/go.mod
deleted file mode 100644
index 870d4f612..000000000
--- a/vendor/golang.org/x/xerrors/go.mod
+++ /dev/null
@@ -1,3 +0,0 @@
-module golang.org/x/xerrors
-
-go 1.11
diff --git a/vendor/golang.org/x/xerrors/internal/internal.go b/vendor/golang.org/x/xerrors/internal/internal.go
deleted file mode 100644
index 89f4eca5d..000000000
--- a/vendor/golang.org/x/xerrors/internal/internal.go
+++ /dev/null
@@ -1,8 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package internal
-
-// EnableTrace indicates whether stack information should be recorded in errors.
-var EnableTrace = true
diff --git a/vendor/golang.org/x/xerrors/wrap.go b/vendor/golang.org/x/xerrors/wrap.go
deleted file mode 100644
index 9a3b51037..000000000
--- a/vendor/golang.org/x/xerrors/wrap.go
+++ /dev/null
@@ -1,106 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package xerrors
-
-import (
-	"reflect"
-)
-
-// A Wrapper provides context around another error.
-type Wrapper interface {
-	// Unwrap returns the next error in the error chain.
-	// If there is no next error, Unwrap returns nil.
-	Unwrap() error
-}
-
-// Opaque returns an error with the same error formatting as err
-// but that does not match err and cannot be unwrapped.
-func Opaque(err error) error {
-	return noWrapper{err}
-}
-
-type noWrapper struct {
-	error
-}
-
-func (e noWrapper) FormatError(p Printer) (next error) {
-	if f, ok := e.error.(Formatter); ok {
-		return f.FormatError(p)
-	}
-	p.Print(e.error)
-	return nil
-}
-
-// Unwrap returns the result of calling the Unwrap method on err, if err implements
-// Unwrap. Otherwise, Unwrap returns nil.
-func Unwrap(err error) error {
-	u, ok := err.(Wrapper)
-	if !ok {
-		return nil
-	}
-	return u.Unwrap()
-}
-
-// Is reports whether any error in err's chain matches target.
-//
-// An error is considered to match a target if it is equal to that target or if
-// it implements a method Is(error) bool such that Is(target) returns true.
-func Is(err, target error) bool {
-	if target == nil {
-		return err == target
-	}
-
-	isComparable := reflect.TypeOf(target).Comparable()
-	for {
-		if isComparable && err == target {
-			return true
-		}
-		if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(target) {
-			return true
-		}
-		// TODO: consider supporing target.Is(err). This would allow
-		// user-definable predicates, but also may allow for coping with sloppy
-		// APIs, thereby making it easier to get away with them.
-		if err = Unwrap(err); err == nil {
-			return false
-		}
-	}
-}
-
-// As finds the first error in err's chain that matches the type to which target
-// points, and if so, sets the target to its value and returns true. An error
-// matches a type if it is assignable to the target type, or if it has a method
-// As(interface{}) bool such that As(target) returns true. As will panic if target
-// is not a non-nil pointer to a type which implements error or is of interface type.
-//
-// The As method should set the target to its value and return true if err
-// matches the type to which target points.
-func As(err error, target interface{}) bool {
-	if target == nil {
-		panic("errors: target cannot be nil")
-	}
-	val := reflect.ValueOf(target)
-	typ := val.Type()
-	if typ.Kind() != reflect.Ptr || val.IsNil() {
-		panic("errors: target must be a non-nil pointer")
-	}
-	if e := typ.Elem(); e.Kind() != reflect.Interface && !e.Implements(errorType) {
-		panic("errors: *target must be interface or implement error")
-	}
-	targetType := typ.Elem()
-	for err != nil {
-		if reflect.TypeOf(err).AssignableTo(targetType) {
-			val.Elem().Set(reflect.ValueOf(err))
-			return true
-		}
-		if x, ok := err.(interface{ As(interface{}) bool }); ok && x.As(target) {
-			return true
-		}
-		err = Unwrap(err)
-	}
-	return false
-}
-
-var errorType = reflect.TypeOf((*error)(nil)).Elem()