Best way to integrate database into Go Web application - mysql

Question

I'm new to developing web applications in Go.
I'm looking for the best way to integrate a MySQL database into my web application.
I was thinking of doing something like this:
type Context struct {
Database *sql.DB
}
// Some database methods like Close() and Query() for Context struct here
In the main function for my web application I would have something like this:
db := sql.Open(...)
ctx := Context{db}
I would then pass then pass my Context structure into various handlers that require a database connection. Would this be a good design decision or is there a better way to integrate a SQL database into my web application?

Answer 1

I typically do something like this:
package main
func main(){
db,err := sql.Open(...)
if err != nil {
log.Fatal(err)
}
defer db.Close()
http.HandleFunc("/feed", server.FeedHandler(db))
http.HandleFunc("/gui", server.GuiHandler(db))
...
log.Fatal(http.ListenAndServe(":8000", nil))
}
Where server is a separate package where I define, implement and test all my http handlers.
This is basically what you were thinking of but skipping the step of wrapping the db in a struct which isn't necessary. I would not recommend making the db a global variable. Having global dependencies will completely destroy any possibility of testing your http handlers in a reliable fashion.
Dependency injecting the db, as in the example above, costs you two extra characters to type every time you call the function but it allows you to test your http handlers easily using the go-sqlmock package which you definitely want to do as your web app grows.
package server
func TestFeedHandler(t *testing.T){
mockdb, err := sqlmock.New()
if err != nil {
t.Errorf("An error '%s' was not expected when opening a stub database connection", err)
}
columns := []string{"id", "name"}
sqlmock.ExpectQuery("SELECT id,name from persons;").
WillReturnRows(sqlmock.NewRows(columns).
AddRow(1234, "bob")
handler := FeedHandler(mockdb)
// test that handler returns expected result
}