Deploy serverless functions to digitalocean in golang

I am trying to build a CRUD in digital ocean serverless functions. I am testing with sqlite3 and insert into the table. When I tried to deploy it to productions, I am getting errors. Here is my code:

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/mattn/go-sqlite3"
)

func Main(args map[string]interface{}) map[string]interface{} {
db, err := sql.Open("sqlite3", "./data.db")
checkErr(err)

// insert
stmt, err := db.Prepare("INSERT INTO userinfo(username, departname, created) values(?,?,?)")
checkErr(err)

res, err := stmt.Exec("rumi", "CSE", "2012-12-09")
checkErr(err)

id, err := res.LastInsertId()
checkErr(err)

fmt.Println(id)

db.Close()

msg := make(map[string]interface{})
msg["body"] = id
return msg
}

Errors I am getting:

➜  functions git:(master) ✗ doctl serverless deploy . --remote-build
Deploying '/home/rumi/go/src/github.com/manjurulhoque/digitalocean-cloud-functions/functions'
  to namespace 'fn-b799454253a-a40440-4639-937f-05102a48c06e'
  on host 'https://fa45as-sgp1-18b45c02afgc.doserverless.co'
Submitted action 'blog/createBlog' for remote building and deployment in runtime go:default (id: b3d5421ee5656bb44c4295421eebb44c642cf)
Submitted action 'sample/hello' for remote building and deployment in runtime go:default (id: b3d5421ee5656bb44c4295421eebb44c642cf)
Submitted action 'blog/db' for remote building and deployment in runtime go:default (id: edcc9eefce9f4aa58c9eefce9f2aa5e6)
Transcript of remote build session for action 'blog/db':
Output of failed build in /tmp/slices/builds/fn-b79956253a-a4080-465639-95637f-05102a48c06e/blog_db/2022-10-22T04-23-08.642Z/packages/blog/db
initializing modules
go: creating new go.mod: module exec
go: to add module requirements and sums:
        go mod tidy
building
db.go:6:2: no required module provides package github.com/mattn/go-sqlite3; to add it:
        go get github.com/mattn/go-sqlite3


Deployed functions ('doctl sbx fn get <funcName> --url' for URL):
  - blog/createBlog
  - sample/hello
Failures:
Error: While deploying action 'blog/db': './build.sh' exited with code 1

project.yml

environment: {}
parameters: {}
packages:
  - name: blog
    environment: {}
    parameters: {}
    annotations: {}
    functions:
      - name: db
        binary: false
        main: ''
        runtime: 'go:default'
        web: true
        parameters: {}
        environment: {}
        annotations: {}
        limits: {}

I didn't find any good resource though to connect to DB. Any help would be appreciated.

In DO, every function itself is an app. So you need to create go.mod and go.sum in each function directoy.

Below is one of my project structure

Note: I wrote an article on how to setup golang app for DO
https://medium.com/@manzurulhoque/use-package-in-digital-ocean-do-serverless-functions-using-golang-cb5200ab22ee