Go build fails when building docker image

Question

I'm a little new to golang and I'm still trying to get my head around the difference between go run main.go and go build [-o] main.go .

I've build a little gin app to try out locally with docker and kubernetes.

package main

import (
    "net/http"

    "github.com/gin-gonic/gin"
)

func main() {

    r := gin.Default()

    r.GET("/healthz", func(c *gin.Context) {
        c.String(http.StatusOK, "")
    })

    r.GET("/readinez", func(c *gin.Context) {
        c.String(http.StatusOK, "")
    })

    r.Run() // listen and serve on 0.0.0.0:8080
} 

The app runs perfectly fine with go run main.go .

My Dockerfile:

FROM golang:latest
RUN mkdir /app
ADD . /app/
WORKDIR /app
RUN go build -o main .
CMD ["/app/main"]

It fails:

It is definitely in there and it also works when I go run main.go . What is the difference to build?

I'm not sure what to do here. Coming from a node background. This does drive a noobie somewhat mad... Sure there is an easy solution.

Answer 1

The program succeeds on your machine because you probably have the gin package installed. You can't assume a container will have it, and should install it explicitly. Just add the following line to your dockerfile before the go build line:

RUN go get github.com/gin-gonic/gin

Answer 2

It may have failed because you used gin, and the library cannot be found inside the container. Try to use glide or godep to vendoring third party library.

Answer 3

go get github.com/gin-gonic/gin

然后它应该工作。

Answer 4

It doenst work for me, still getting

[6/6] RUN go build -o bin/app cmd/app/main.go:
#10 0.171 go: github.com/gin-gonic/gin@v1.8.1 requires
#10 0.171 github.com/go-playground/validator/v10@v10.10.0: missing go.sum entry; to add it: #10 0.171 go mod download github.com/go-playground/validator/v10

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