Go build: cannot find package, although GOPATH and modules are configured

Hello, colleagues! I'm new to Go and have been struggling with a problem for the second day. I wrote a simple program that uses an external package for working with JSON (e.g., `github.com/tidwall/gjson`). I installed Go 1.22 on Ubuntu, created a folder `~/go_projects/myapp`, and inside it — a file `main.go`. Here is my code: ```go package main import ( "fmt" "github.com/tidwall/gjson" ) func main() { json := `{"name": "Alice", "age": 30}` value := gjson.Get(json, "name") fmt.Println(value.String()) } ``` I ran `export GOPATH=$HOME/go` and `export PATH=$PATH:$GOPATH/bin`, then ran `go mod init myapp` in the project folder. After that I tried `go build`, but got the error: ``` build command-line-arguments: cannot find package "github.com/tidwall/gjson" in any of: /