add nolint skip support

Author: kkHAIKE

README.md

@@ -94,6 +94,23 @@ func NoInheritCancel(_ context.Context) (context.Context,context.CancelFunc) {
 }
 ```
 
+You can add `// nolint: contextcheck` in function decl doc comment, to skip this linter in some false-positive case.
+
+```go
+// nolint: contextcheck
+func call1() {
+    doSomeThing(context.Background()) // add nolint will no issuss for that
+}
+
+func call2(ctx context.Context) {
+    call1()
+}
+
+func call3() {
+    call2(context.Background())
+}
+```
+
 ## Installation
 
 You can get `contextcheck` by `go get` command.

contextcheck.go

@@ -3,6 +3,7 @@ package contextcheck
 import (
 	"go/ast"
 	"go/types"
+	"regexp"
 	"strconv"
 	"strings"
 	"sync"
@@ -239,9 +240,41 @@ func (r *runner) checkIsEntry(f *ssa.Function) entryType {
 		return EntryWithHttpHandler
 	}
 
+	if r.skipByNolint(f) {
+		return EntryNone
+	}
+
 	return EntryNormal
 }
 
+var nolintRe = regexp.MustCompile(`^//\s?nolint:`)
+
+func (r *runner) skipByNolint(f *ssa.Function) bool {
+	file := analysisutil.File(r.pass, f.Pos())
+	if file == nil {
+		return false
+	}
+
+	// only support FuncDecl comment
+	var fd *ast.FuncDecl
+	for _, v := range file.Decls {
+		if tmp, ok := v.(*ast.FuncDecl); ok && tmp.Name.Pos() == f.Pos() {
+			fd = tmp
+			break
+		}
+	}
+	if fd == nil || fd.Doc == nil || len(fd.Doc.List) == 0 {
+		return false
+	}
+
+	for _, v := range fd.Doc.List {
+		if len(nolintRe.FindString(v.Text)) > 0 && strings.Contains(v.Text, "contextcheck") {
+			return true
+		}
+	}
+	return false
+}
+
 func (r *runner) checkIsCtx(f *ssa.Function) (in, out bool) {
 	// check params
 	tuple := f.Signature.Params()

testdata/src/a/a.go

@@ -109,6 +109,11 @@ func f10(in bool, w http.ResponseWriter, r *http.Request) {
 	f8(context.Background(), w, r)
 }
 
+// nolint: contextcheck
+func f14(w http.ResponseWriter, r *http.Request, err error) {
+	f8(r.Context(), w, r)
+}
+
 func f11() {
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		f8(r.Context(), w, r)
@@ -118,6 +123,8 @@ func f11() {
 
 		// f10 should be like `func f10(ctx context.Context, in bool, w http.ResponseWriter, r *http.Request)`
 		f10(true, w, r) // want "Function `f10` should pass the context parameter"
+
+		f14(w, r, nil)
 	})
 }