argument.go

// in this case we inject the database as argument to another package

package httpd

import (
    "net/http"
    "path/to/db"
)

var db *db.Database

func Setup(d *db.Database) {
    db = d

    http.HandleFunc("/", handle)
    http.ListenAndServe(":3000", nil)
}

func handle(w http.ResponseWriter, r *http.Request) {
    data, err := db.FindAll()

    w.WriteHeader(200)
    w.Write(data)
}

factory.go

// in this use case we create an extra database with setup

package httpd

import (
    "net/http"
    "path/to/db"
)

var db *db.Database

func Setup() {
    db = db.New()

    http.HandleFunc("/", handle)
    http.ListenAndServe(":3000", nil)
}

func handle(w http.ResponseWriter, r *http.Request) {
    data, err := db.FindAll()

    w.WriteHeader(200)
    w.Write(data)
}

global.go

// in this case the "db" package exports a global variable we use in our handle

package httpd

import (
    "net/http"
    "path/to/db"
)

func Setup() {
    http.HandleFunc("/", handle)
    http.ListenAndServe(":3000", nil)
}

func handle(w http.ResponseWriter, r *http.Request) {
    data, err := db.Db.FindAll()

    w.WriteHeader(200)
    w.Write(data)
}

singleton.go

// in this case the "db" package has a local instance of "Database" which can be accessed through exported functions

package httpd

import (
    "net/http"
    "path/to/db"
)

func Setup() {
    http.HandleFunc("/", handle)
    http.ListenAndServe(":3000", nil)
}

func handle(w http.ResponseWriter, r *http.Request) {
    data, err := db.FindAll()

    w.WriteHeader(200)
    w.Write(data)
}