internal: Add compatcontext.WithoutCancel

Copy the implementation of `context.WithoutCancel` introduced in Go 1.21
to be able to use it when building with older versions.
This will use the stdlib directly when building with Go 1.21+.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

internal/compatcontext/cancel.go

@@ -0,0 +1,89 @@
+//go:build !go1.21
+
+// 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
+// met:
+//
+//   - Redistributions of source code must retain the above copyright
+//
+// notice, this list of conditions and the following disclaimer.
+//   - Redistributions in binary form must reproduce the above
+//
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//   - Neither the name of Google Inc. nor the names of its
+//
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Source: https://cs.opensource.google/go/go/+/refs/tags/go1.21.1:src/context/context.go
+// The only modifications to the original source were:
+// - replacing the usage of internal reflectlite with reflect
+// - replacing the usage of private value function with Value method call
+package compatcontext // import "github.com/docker/docker/internal/compatcontext"
+
+import (
+	"context"
+	"reflect"
+	"time"
+)
+
+// WithoutCancel returns a copy of parent that is not canceled when parent is canceled.
+// The returned context returns no Deadline or Err, and its Done channel is nil.
+// Calling [Cause] on the returned context returns nil.
+func WithoutCancel(parent context.Context) context.Context {
+	if parent == nil {
+		panic("cannot create context from nil parent")
+	}
+	return withoutCancelCtx{parent}
+}
+
+type withoutCancelCtx struct {
+	c context.Context
+}
+
+func (withoutCancelCtx) Deadline() (deadline time.Time, ok bool) {
+	return
+}
+
+func (withoutCancelCtx) Done() <-chan struct{} {
+	return nil
+}
+
+func (withoutCancelCtx) Err() error {
+	return nil
+}
+
+func (c withoutCancelCtx) Value(key any) any {
+	return c.c.Value(key)
+}
+
+func (c withoutCancelCtx) String() string {
+	return contextName(c.c) + ".WithoutCancel"
+}
+
+type stringer interface {
+	String() string
+}
+
+func contextName(c context.Context) string {
+	if s, ok := c.(stringer); ok {
+		return s.String()
+	}
+	return reflect.TypeOf(c).String()
+}

internal/compatcontext/cancel_go121.go

@@ -0,0 +1,9 @@
+//go:build go1.21
+
+package compatcontext // import "github.com/docker/docker/internal/compatcontext"
+
+import "context"
+
+func WithoutCancel(ctx context.Context) context.Context {
+	return context.WithoutCancel(ctx)
+}