strings: TrimRight() is not entirely right #46885

What version of Go are you using (go version)?

Playground go1.16.5

Does this issue reproduce with the latest release?

What operating system and processor architecture are you using (go env)?

Playground whatever.

What did you do?

Playground link

package main

import (
	"fmt"
	"strings"
	"runtime"
)

func main() {
	println(runtime.Version())

	ss := []string{ `Core.go`, `DebugInfo.go`, `Verifier.go` }
	sfx := `.go`
for _, s := range ss {
	s_ := strings.TrimRight(s, sfx)
	fmt.Println(s_)
}
}

What did you expect to see?

go1.16.5
Core
DebugInfo
Verifier

What did you see instead?

go1.16.5
Core
DebugInf
Verifier