Improved code style

src/expression/bench_test.go

@@ -11,7 +11,7 @@ func BenchmarkExpression(b *testing.B) {
 	src := []byte("(1+2-3*4)+(5*6-7+8)")
 	tokens := token.Tokenize(src)
 
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		expression.Parse(tokens)
 	}
 }