strings.Join vs fmt.Sprintf vs string concat (+)

join_test.go

package join

import (
	"fmt"
	"strings"
	"testing"
)

var (
	testData = []string{"a", "b", "c", "d", "e"}
)

func BenchmarkJoin(b *testing.B) {
	for i := 0; i < b.N; i++ {
		s := strings.Join(testData, ":")
		_ = s
	}
}

func BenchmarkSprintf(b *testing.B) {
	for i := 0; i < b.N; i++ {
		s := fmt.Sprintf("%s:%s:%s:%s:%s", testData[0], testData[1], testData[2], testData[3], testData[4])
		_ = s
	}
}

func BenchmarkConcat(b *testing.B) {
	for i := 0; i < b.N; i++ {
		s := testData[0] + ":" + testData[1] + ":" + testData[2] + ":" + testData[3] + ":" + testData[4]
		_ = s
	}
}

Test results on MacBook Pro (awesomeProject is the default name for a new Goland project)

goos: darwin
goarch: amd64
pkg: awesomeProject/join
BenchmarkJoin-8         20000000                94.3 ns/op
BenchmarkSprintf-8       5000000               375 ns/op
BenchmarkConcat-8       20000000                67.5 ns/op
PASS
ok      awesomeProject/join     5.667s