golang中.a文件是什么

package mainimport "C"import (
    //"fmt"
    "github.com/tuotoo/qrcode"
    "os")//export GetQrcodeStringfunc GetQrcodeString(cstring *C.char) *C.char {
    //func GetQrcodeString() *C.char {
    path := C.GoString(cstring)
    //path := "qrcode.png"
    fi, err := os.Open(path)
    if err != nil {
        //fmt.Println(err.Error())
        return C.CString(path)
    }
    defer fi.Close()
    qrmatrix, err := qrcode.Decode(fi)
    if err != nil {
        //fmt.Println(err.Error())
        return C.CString(path)
    }
    //fmt.Println(qrmatrix.Content)
    //return C.Cstring(qrmatrix.Content)
    gostr := qrmatrix.Content
    cstr := C.CString(gostr)
    return cstr}func main() {}

go build -buildmode=c-archive -o pkgqrcode.a pkgqrcode.go