cl/_testlibgo: bytes strings

cl/_testlibgo/strings/in.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"strings"
+	"unicode"
+)
+
+func main() {
+	var b strings.Builder
+	b.Write([]byte("Hello "))
+	b.WriteString("World")
+
+	println("len:", b.Len(), "cap:", b.Cap(), "string:", b.String())
+
+	f := func(c rune) bool {
+		return unicode.Is(unicode.Han, c)
+	}
+	println(strings.IndexFunc("Hello, 世界", f))
+	println(strings.IndexFunc("Hello, world", f))
+}