c_printf.c

#include <stdio.h>

int main()
{
    int i;
    for (i = 0; i < 500000; ++i) {
        fprintf(stdout, "this is a test from error");
    }
    return 0;
}

go_printf.go

package main

import "fmt"

func main() {
    for i := 0; i < 500000; i++ {
        fmt.Printf("this is a test from error");
    }
}

output

real    0m0.054s
user    0m0.017s
sys     0m0.037s
       0  2500001 12500000 output

real    0m1.861s
user    0m0.230s
sys     0m1.627s
       0  2500001 12500000 output

run.sh

#!/bin/bash

gcc c_printf.c -O2 -o c_printf
go build go_printf.go

time ./c_printf > output
wc output

time ./go_printf > output
wc output

The comparable c version should be

include <stdio.h>

int main()
{
int i;
for (i = 0; i < 500000; ++i) {
fprintf(stdout, "this is a test from error %d", i);
fflush(stdout);
}
return 0;
}

Go printf do not have buffer, it will write to fd each time you call it.
If you want to use bufio, refer http://golang.org/pkg/bufio/.

package main

import "fmt"
import "os"

func main() {
for i := 0; i < 500000; i++ {
fmt.Fprintf(os.Stdout, "this is a test from error %d", i);
}
}