MongoDB Atlas: Go driver connection with context timeouts

Go driver + Atlas

package main

import (
    "context"
    "os"
    "time"

    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

func connectDB() (*mongo.Client, error) {
    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()

    client, err := mongo.Connect(ctx,
        options.Client().
            ApplyURI(os.Getenv("MONGODB_URI")).
            SetMaxPoolSize(20).
            SetServerSelectionTimeout(5*time.Second),
    )
    if err != nil {
        return nil, err
    }
    if err := client.Ping(ctx, nil); err != nil {
        return nil, err
    }
    return client, nil
}

Rules

• Always pass a context with a timeout to Connect and Ping. Without it a bad network path hangs forever.
• ApplyURI parses the Atlas SRV string including credentials and options. Do not hand-assemble hosts.
• Share the returned *mongo.Client across goroutines; it is safe for concurrent use and owns the pool.
• On shutdown call client.Disconnect(ctx) so pooled connections close cleanly instead of lingering until the server times them out.
• SetMaxPoolSize caps total connections. Size it from expected concurrent operations, not from wishful thinking.

Verify

Ping succeeding from the deploy network proves URI, credentials, and IP access list in one shot.

Go driver connection options (ApplyURI, context timeouts, pool sizing) verified against the MongoDB connection string reference at https://www.mongodb.com/docs/manual/reference/connection-string/; Atlas-side prerequisites (IP access list, database user) per https://www.mongodb.com/docs/atlas/troubleshoot-connection/, checked 2026-09-26.