cmd/go/internal: use strings.CutSuffix

Updates #42537

Change-Id: I2d4c5e911c8a2ddfe9a976896b05d3cd8be61f6b
GitHub-Last-Rev: a87597d
GitHub-Pull-Request: #55830
Reviewed-on: https://go-review.googlesource.com/c/go/+/433275
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Benny Siegert <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>

Author: cuishuang

src/cmd/go/internal/clean/clean.go

@@ -340,16 +340,14 @@ func clean(p *load.Package) {
 			continue
 		}
 
-		if strings.HasSuffix(name, "_test.go") {
-			base := name[:len(name)-len("_test.go")]
+		if base, found := strings.CutSuffix(name, "_test.go"); found {
 			allRemove = append(allRemove, base+".test", base+".test.exe")
 		}
 
-		if strings.HasSuffix(name, ".go") {
+		if base, found := strings.CutSuffix(name, ".go"); found {
 			// TODO(adg,rsc): check that this .go file is actually
 			// in "package main", and therefore capable of building
 			// to an executable file.
-			base := name[:len(name)-len(".go")]
 			allRemove = append(allRemove, base, base+".exe")
 		}
 	}

src/cmd/go/internal/load/pkg.go

@@ -3115,10 +3115,10 @@ func PackagesAndErrorsOutsideModule(ctx context.Context, opts PackageOpts, args
 	}
 	patterns := make([]string, len(args))
 	for i, arg := range args {
-		if !strings.HasSuffix(arg, "@"+version) {
+		p, found := strings.CutSuffix(arg, "@"+version)
+		if !found {
 			return nil, fmt.Errorf("%s: all arguments must refer to packages in the same module at the same version (@%s)", arg, version)
 		}
-		p := arg[:len(arg)-len(version)-1]
 		switch {
 		case build.IsLocalImport(p):
 			return nil, fmt.Errorf("%s: argument must be a package path, not a relative path", arg)