package main

import (
	"compress/gzip"
	"io/ioutil"
	"log"
	"os"
)

func main() {
	name := os.Args[1]
	f, err := os.Open(name)
	if err != nil {
		log.Fatal(err)
	}
	r, err := gzip.NewReader(f)
	if err != nil {
		log.Fatal(err)
	}
	b, err := ioutil.ReadAll(r)
	if err != nil {
		log.Fatal(err)
	}
	os.Stdout.Write(b)
}

cd noracedetector
vim main.go # write the above code
go install
cd ../
mv noracedetector racedetector
cd racedetector
go install -race

$ time noracedetector GeoLite2-City.mmdb.gz > /dev/null

real    0m0.877s
user    0m0.780s
sys     0m0.095s
$ time racedectector GeoLite2-City.mmdb.gz > /dev/null

real    0m18.344s
user    0m15.998s
sys     0m0.678s

go version go1.9.2 darwin/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/voutasaurus/go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/v_/gz6l428x5w97h0zrm5m03rlm0000gn/T/go-build431950117=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOROOT/bin/go version: go version go1.9.2 darwin/amd64
GOROOT/bin/go tool compile -V: compile version go1.9.2
uname -v: Darwin Kernel Version 15.6.0: Mon Oct  2 22:20:08 PDT 2017; root:xnu-3248.71.4~1/RELEASE_X86_64
ProductName:	Mac OS X
ProductVersion:	10.11.6
BuildVersion:	15G17023
lldb --version: lldb-360.1.70