golang 引用其它目录的包

源码目录：

root@VM-0-12-ubuntu:~/go-path/src/test# pwd
/root/go-path/src/test
root@VM-0-12-ubuntu:~/go-path/src/test# tree
.
├── go.mod
├── hello
│   └── hello.go
└── main.go

1 directory, 3 files
root@VM-0-12-ubuntu:~/go-path/src/test#

main.go

package main

import (
        "fmt"
        "test/hello"
)

func main() {
        hello.Hello()
        fmt.Println("aa")
}

hello/hello.go

package hello

import (
        "fmt"
)

func Hello() {
        fmt.Println("hello api")
}

环境：

root@VM-0-12-ubuntu:~/go-path/src/test# go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/root/go-path/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/root/go-path"
GOPRIVATE=""
GOPROXY="https://goproxy.io"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/root/go-path/src/test/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build614597735=/tmp/go-build -gno-record-gcc-switches"
root@VM-0-12-ubuntu:~/go-path/src/test# 

编译运行：

root@VM-0-12-ubuntu:~/go-path/src/test# go build
root@VM-0-12-ubuntu:~/go-path/src/test# ./test 
hello api
aa
root@VM-0-12-ubuntu:~/go-path/src/test#