runtime: using bytes.CutPrefix

Change-Id: I3f2dae17496b5b4efbdc022802f941a616abd87a
Reviewed-on: https://go-review.googlesource.com/c/go/+/435276
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/runtime/testdata/testprog/traceback_ancestors.go b/src/runtime/testdata/testprog/traceback_ancestors.go
index 1d0d00bab7d4ae48cc8fd81d7bd33e9e90e3debe..8fc1aa7dbbfdec509a26267f49735585606abbf2 100644 (file)
--- a/src/runtime/testdata/testprog/traceback_ancestors.go
+++ b/src/runtime/testdata/testprog/traceback_ancestors.go
@@ -87,9 +87,10 @@ func goroutineID() string {
        buf := make([]byte, 128)
        runtime.Stack(buf, false)
        prefix := []byte("goroutine ")
-       if !bytes.HasPrefix(buf, prefix) {
+       var found bool
+       if buf, found = bytes.CutPrefix(buf, prefix); !found {
                panic(fmt.Sprintf("expected %q at beginning of traceback:\n%s", prefix, buf))
        }
-       id, _, _ := bytes.Cut(bytes.TrimPrefix(buf, prefix), []byte(" "))
+       id, _, _ := bytes.Cut(buf, []byte(" "))
        return string(id)
 }