go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/ttacon/chalk: exec: "git": executable file not found in  %PATH%

我的环境：

set GOARCH=amd64
set GOBIN=
set GOEXE=.exe
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=windows
set GOPATH=F:\Works\Go
set GORACE=
set GOROOT=C:\Go
set GOTOOLDIR=C:\Go\pkg\tool\windows_amd64
set GO15VENDOREXPERIMENT=1
set CC=gcc
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0
set CXX=g++
set CGO_ENABLED=1

我的Go环境出了什么问题？