GoLang custom package import problem

php editor Xinyi is here to introduce to you a common problem in GoLang: custom package import problem. In Go language development, we often need to use custom packages to implement some specific functions. However, when importing custom packages, some problems sometimes occur, such as package cannot be found, package name conflicts, etc. This article will answer these questions in detail and provide solutions to help developers better handle custom package import problems and improve development efficiency.

Question content

I am learning golang and encountered a problem.

I used go mod init main to create the mod file

Next I created the controller and routing folders as shown below:

├── contollers
│   └── users.controller.go
├── routes
│   ├── index.go
│   └── users.routes.go
├── vendor
│   └── modules.txt
├── go.mod
├── go.sum
└── main.go

In the mod file, the module looks like this Module main

Now when I try to import the controller into the router it gives me an import error.

I have been doing the following. Try - 1

import (
    "$gopath/controllers"

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

It gives invalid import path: "$gopath/controllers" syntax error

Try - 2

import (
    "$gopath/main/controllers"

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

Same error

Try - 3

import (
    "main/controllers"

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

Controller.go

package controllers;

import (
    "fmt"

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

func healthcheck() gin.handlerfunc {
    return func (c *gin.context)  {
        fmt.println("reached controller")
    }
}

router.go

package routes

import (
    "bootcamp.com/server/controllers"

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

func UserRouters(inComingRoutes *gin.Engine) {
    inComingRoutes.GET("/api/health", controllers.HealthCheck());
}

Throws this error, Unable to import main/controllers (no required module provides package "main/controllers")

I've been stuck with this issue for 3-4 hours, can someone please suggest me how to import this controller into my routes.

Thanks in advance.

Solution

1. Modify the module path by editing go.mod:

- module main
+ module example.com/hello

1. Modify the import path:

import (
-     "main/controllers"
+     "example.com/hello/controllers"

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

1. controller.go (remove trailing ;):

- package controllers;
+ package controllers

1. Rename directory contollers to controllers to match the package name (missing r).

2. Delete the vendor folder.

illustrate:

1. main has a special meaning in go. Quoted from golang specification:

A complete program is created by transitively linking a single unimported package named main package with all its imported packages. The main package must have the package name main and declare a function main that takes no parameters and returns no value.

1. Import paths without dots are reserved for the standard library and go toolchain. See documentation cmd/go: Preserving module names without dots.

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