update log_test.go benchmark case and update doc

Author: zbh255

README.md

@@ -37,15 +37,14 @@ pkg: github.com/zbh255/bilog
 cpu: Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz
 BenchmarkLogger
 BenchmarkLogger/BiLog
-BenchmarkLogger/BiLog-8         										20721610	        55.23 ns/op	       0 B/op	       0 allocs/op
-BenchmarkLogger/BiLogDoubleSwitchPrefix
-BenchmarkLogger/BiLogDoubleSwitchPrefix-8         	10265996	       112.8 ns/op	       0 B/op	       0 allocs/op
+BenchmarkLogger/BiLog-8         	20940777	        58.74 ns/op	       0 B/op	       0 allocs/op
+BenchmarkLogger/BiLogDouble
+BenchmarkLogger/BiLogDouble-8   	10824482	       104.2 ns/op	       0 B/op	       0 allocs/op
 BenchmarkLogger/StdLog
-BenchmarkLogger/StdLog-8                          	 3658471	       313.2 ns/op	      16 B/op	       1 allocs/op
-BenchmarkLogger/StdLogDoubleSwitchPrefix
-BenchmarkLogger/StdLogDoubleSwitchPrefix-8        	 1850556	       642.7 ns/op	      32 B/op	       2 allocs/op
+BenchmarkLogger/StdLog-8        	 3951027	       297.6 ns/op	      16 B/op	       1 allocs/op
+BenchmarkLogger/StdLogDouble
+BenchmarkLogger/StdLogDouble-8  	 1948030	       630.0 ns/op	      32 B/op	       2 allocs/op
 PASS
-
 ```
 
 ## Lisence

log_test.go

@@ -43,9 +43,10 @@ func BenchmarkLogger(b *testing.B) {
 		logger := NewLogger(&TestWriter{}, PANIC)
 		for i := 0; i < b.N; i++ {
 			logger.Debug("hello world")
+			logger.Flush()
 		}
 	})
-	b.Run("BiLogDoubleSwitchPrefix", func(b *testing.B) {
+	b.Run("BiLogDouble", func(b *testing.B) {
 		b.ReportAllocs()
 		logger := NewLogger(&TestWriter{}, PANIC)
 		for i := 0; i < b.N; i++ {
@@ -61,7 +62,7 @@ func BenchmarkLogger(b *testing.B) {
 			logger.Print("hello world")
 		}
 	})
-	b.Run("StdLogDoubleSwitchPrefix", func(b *testing.B) {
+	b.Run("StdLogDouble", func(b *testing.B) {
 		b.ReportAllocs()
 		logger := log.New(&TestWriter{}, "[Error] ", log.LstdFlags)
 		for i := 0; i < b.N; i++ {