Docker Go 映像：启动容器进程导致：exec：“app”：在 $PATH 中找不到可执行文件：未知

Question

I have been reading a lot of similar issues on different languages, none of them are Go.

I just created a Dockerfile with the instructions I followed on official Docker hub page :

FROM golang:1.17.3

WORKDIR /go/src/app
COPY . .

RUN go get -d -v ./...
RUN go install -v ./...

CMD ["app"]

This is my folder structure:

users-service
 |-> .gitignore
 |-> Dockerfile
 |-> go.mod
 |-> main.go
 |-> README.md

If anyone needs to see some code, this is how my main.go looks like:

package main

import "fmt"

func main() {
    fmt.Println("Hello, World!")
}

1. I ran docker build -t users-service. :

$ docker build -t users-service .
[+] Building 5.5s (11/11) FINISHED
 => [internal] load build definition from Dockerfile                                                                                                               0.1s
 => => transferring dockerfile: 154B                                                                                                                               0.1s 
 => [internal] load .dockerignore                                                                                                                                  0.0s 
 => => transferring context: 2B                                                                                                                                    0.0s 
 => [internal] load metadata for docker.io/library/golang:1.17.3                                                                                                   3.3s
 => [auth] library/golang:pull token for registry-1.docker.io                                                                                                      0.0s
 => [1/5] FROM docker.io/library/golang:1.17.3@sha256:6556ce40115451e40d6afbc12658567906c9250b0fda250302dffbee9d529987                                             0.3s
 => [internal] load build context                                                                                                                                  0.1s 
 => => transferring context: 2.05kB                                                                                                                                0.0s 
 => [2/5] WORKDIR /go/src/app                                                                                                                                      0.1s
 => [3/5] COPY . .                                                                                                                                                 0.1s
 => [4/5] RUN go get -d -v ./...                                                                                                                                   0.6s 
 => [5/5] RUN go install -v ./...                                                                                                                                  0.7s 
 => exporting to image                                                                                                                                             0.2s 
 => => exporting layers                                                                                                                                            0.1s 
 => => writing image sha256:1f0e97ed123b079f80eb259dh3e34c90a48bf93e8f55629d05044fec8bfcaca6                                                                       0.0s 
 => => naming to docker.io/library/users-service                                                                                                                   0.0s 

Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them

2. Then I ran docker run users-service but I get that error:

$ docker run users-service

docker: Error response from daemon: OCI runtime create failed: container_linux.go:380: starting container process caused: exec: "app": executable file not found in $PATH: unknown.

I remember I had some troubles with GOPATH environment variable in Visual Studio Code on Windows, maybe it's related... Any sugguestions?

Answer 1

Your "app" executable binary should be available in your $PATH to call globally without any path prefix. Otherwise, you have to supply your full path to your executable like CMD ["/my/app"]

Also, I recommend using an ENTRYPOINT instruction. ENTRYPOINT indicates the direct path to the executable, while CMD indicates arguments supplied to the ENTRYPOINT .

Using combined RUN instructions make your image layers minimal, your overall image size becomes little bit smaller compared to using multiple RUN s.

Answer 2

The official Docker documentation has useful instructions for building a Go image: https://docs.docker.com/language/golang/build-images/

---

In summary, you need to build your Go binary and you need to configure the CMD appropriately, eg:

FROM golang:1.17.3

WORKDIR /app

COPY main.go .
COPY go.mod ./

RUN go build -o /my-go-app

CMD ["/my-go-app"]

Build the container:

$ docker build -t users-service .

Run the docker container:

$ docker run --rm -it users-service
Hello, World!