在docker容器中运行时，golang项目找不到依赖项

Question

I have this golang sandbox project: https://github.com/cflynn07/golang-db-gateway-example

When I try to run gateway/gateway.go inside a golang:1.6.0-alpine

~/g/s/g/c/golang-db-gateway-example git:master ❯❯❯ docker-compose up gateway
mysql_server is up-to-date
Starting gateway
Attaching to gateway
gateway | gateway.go:7:2: cannot find package "github.com/go-sql-driver/mysql" in any of:
gateway |   /usr/local/go/src/github.com/go-sql-driver/mysql (from $GOROOT)
gateway |   /go/src/github.com/go-sql-driver/mysql (from $GOPATH)
gateway | gateway.go:8:2: cannot find package "github.com/gorilla/mux" in any of:
gateway |   /usr/local/go/src/github.com/gorilla/mux (from $GOROOT)
gateway |   /go/src/github.com/gorilla/mux (from $GOPATH)
gateway exited with code 1

Why isn't the build step detecting my project's dependencies inside the /example/vendor folder?

When I run go run gateway/gateway.go from my host OS, the command works.

Directory structure (mounted inside container at /example)

~/g/s/g/c/golang-db-gateway-example git:master ❯❯❯ tree -L 3
.
├── README.md
├── client
│   └── client.go
├── docker-compose.yml
├── gateway
│   └── gateway.go
├── glide.lock
├── glide.yaml
├── tmp
└── vendor
    └── github.com
        ├── go-sql-driver
        └── gorilla

---

Relevant files:

docker-compose.yml

mysql:
  container_name: mysql_server
  image: mysql:5.7.11
  environment:
    - MYSQL_ROOT_PASSWORD=root
  ports:
    - 3306
gateway:
  container_name: gateway
  image: golang:1.6.0-alpine
  volumes:
    - ./:/example
  working_dir: /example/gateway
  command: go run gateway.go
  environment:
    - MYSQL_ROOT_PASSWORD=root
    - MYSQL_DATABASE=sandbox
  links:
    - mysql

gateway/gateway.go

package main

import (
    "database/sql"
    "encoding/json"
    "fmt"
    _ "github.com/go-sql-driver/mysql"
    "github.com/gorilla/mux"
    "net/http"
    "os"
)

var db *sql.DB

func main() {
    r := mux.NewRouter()

    var e error
    db, e = sql.Open(
        "mysql", os.ExpandEnv("root:${MYSQL_SERVER_PASSWORD}@mysql_server:3306/${MYSQL_DATABASE}"))
    fmt.Print("error is", e)

    r.HandleFunc("/todos", getTodos).Methods("GET")

    http.ListenAndServe(":8080", r)
    fmt.Printf("gateway")
}

type todo struct{}

func getTodos(w http.ResponseWriter, r *http.Request) {
    t := new(todo)
    s, _ := json.Marshal(t)
    w.Header().Set("Content-Type", "application/json; charset=UTF-8")
    fmt.Fprint(w, string(s))
}

Update 1 I changed my data-volume mount path inside the container to mount the project under the containers $GOPATH

mysql:
  container_name: mysql_server
  image: mysql:5.7.11
  environment:
    - MYSQL_ROOT_PASSWORD=root
  ports:
    - 3306
gateway:
  container_name: gateway
  image: golang:1.6.0-alpine
  volumes:
    - ./:/go/src/github.com/cflynn07/golang-db-gateway-example
  working_dir: /go/src/github.com/cflynn07/golang-db-gateway-example
  command: go run gateway/gateway.go
  environment:
    - MYSQL_ROOT_PASSWORD=root
    - MYSQL_DATABASE=sandbox
  links:
    - mysql

However now docker appears to hang:

~/g/s/g/c/golang-db-gateway-example git:master ❯❯❯ docker-compose up gateway                                                         ✱
mysql_server is up-to-date
Recreating gateway
Attaching to gateway

Answer 1

Actually you successfully got the Go server running. It wasn't hanging, just waiting for connections. Due to some quirks, there's no output: it didn't attempt to connect to the database, and logging statements were buffered.

Try modifying gateway.go main:

func main() {
    log.Println("Starting main...")

    conn := os.ExpandEnv("root:${MYSQL_SERVER_PASSWORD}@mysql_server:3306/${MYSQL_DATABASE}")

    var err error
    db, err = sql.Open("mysql", conn)
    if err != nil {
        log.Fatal(err)
    }

    log.Println("pinging", conn)
    if err := db.Ping(); err != nil {
        log.Fatal(err)
    }

    r := mux.NewRouter()
    r.HandleFunc("/todos", getTodos).Methods("GET")

    listen := ":8080"
    log.Printf("Listening on %s
", listen)
    log.Fatal(http.ListenAndServe(listen, r))
}

Running this version gives:

$ docker-compose up gateway
mysql_server is up-to-date
Starting gateway
Attaching to gateway
gateway | 2016/03/15 10:58:05 Starting main...
gateway | 2016/03/15 10:58:05 pinging root:@mysql_server:3306/sandbox
gateway | 2016/03/15 10:58:05 default addr for network 'mysql_server:3306' unknown
gateway | exit status 1
gateway exited with code 1

You should be good to go from there. Note:

• docker-compose seems to buffer standard output until newline
• log functions such as log.Print add newlines, fmt.Print doesn't
• sql.Open doesn't connect to the database, use sql.Ping (see wiki)
• MYSQL_SERVER_PASSWORD is missing
• network type of the mysql connection string is missing (see examples)
• start mysql server too
• need to create new or mount existing database 'sandbox'

Hope that helps.