Original: http://play.golang.org/p/dmh1FkGNO- See: http://saml.rilspace.org/moar-languagez-gc-content-in-python-d-fpc-c-and-c

gc_rp.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
)

func main() {
	countat := [256]int{
		'A': 1,
		'T': 1,
	}
	countgc := [256]int{
		'G': 1,
		'C': 1,
	}
	gc := 0
	at := 0
	file, err := os.Open("Homo_sapiens.GRCh37.67.dna_rm.chromosome.Y.fa")
	if err != nil {
		log.Fatal(err)
	}
	scan := bufio.NewScanner(file)
	for scan.Scan() {
		line := scan.Bytes()
		if len(line) == 0 || line[0] == '>' {
			continue
		}
		for _, c := range line {
			gc += countgc[c]
			at += countat[c]
		}
	}
	gcFraction := float32(gc) / float32(at+gc)
	fmt.Println(gcFraction * 100)
}