在Go中连接到多个数据库的最佳做法是什么？

Question

I am trying to understand if the following is good or bad practice.

If it turns out that this is good / normal practice, it makes it easier for me to implement multiple database connectors into my project.

Situation: I have created an API server and every time a call is done to the API this piece of code runs:

ctx := context.Background()

client, err := datastore.NewClient(ctx, "foobar")
if err != nil {
    log.Fatalf("Failed to create client: %v", err)
}

The service gets many requests per second and I'm not sure if I should run the newClient() function only once on startup, or every time the API is called.

PS:
The same would go if another connector would be MySQL. Every time the API gets a request, the following code will run:

db, err = sql.Open("mysql", "yourusername:yourpassword@/yourdatabase")
if err != nil {
    panic(err.Error())    
}

Answer 1

I'm not sure about datastore.Client, but database.DB manages a pool of connections, is safe for concurrent use, and you shouldn't really call db.Open every time you want to execute a query. In fact, the last paragraph from Open's documentation states that clearly.

The returned DB is safe for concurrent use by multiple goroutines and maintains its own pool of idle connections. Thus, the Open function should be called just once. It is rarely necessary to close a DB.

Update:

If you take a look at the comment in the example code of the Basic Operations section in the datastore's documentation, you'll find the recommended use.

Create a datastore client. In a typical application, you would create a single client which is reused for every datastore operation.