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Before You Get Started

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This tutorial assumes you have:

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In this tutorial, we will use the official MongoDB Go Driver to manage our MongoDB database. In the due process, we will write a program to learn how to install the MongoDB Go Driver and perform CRUD operations with it.

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Installation

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First in an empty folder run the below command

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go mod init gomongo
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go mod init creates a new go.mod file and automatically imports dependencies when you will run go program. Then create the file main.go and write the below code, We will explain what this code will do in a min.

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package main\n\nimport (\n    "context"\n    "fmt"\n    "log"\n\n    "go.mongodb.org/mongo-driver/bson"\n    "go.mongodb.org/mongo-driver/mongo"\n    "go.mongodb.org/mongo-driver/mongo/options"\n)\n\n// Book - We will be using this Book type to perform crud operations\ntype Book struct {\n  Title     string\n  Author    string\n  ISBN      string\n  Publisher string\n  Copies     int\n}\n\nfunc main() {\n    \n  // Set client options\n  clientOptions := options.Client().ApplyURI("mongodb://localhost:27017")\n\n  // Connect to MongoDB\n  client, err := mongo.Connect(context.TODO(), clientOptions)\n\n  if err != nil {\n    log.Fatal(err)\n  }\n\n  // Check the connection\n  err = client.Ping(context.TODO(), nil)\n\n  if err != nil {\n    log.Fatal(err)\n  }\n\n  fmt.Println("Connected to MongoDB!")\n  booksCollection := client.Database("testdb").Collection("books")\n}
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In the above code, we have imported the bson, mongo, and mongo/options packages of mongo-driver and defined a Book type which will be used in this tutorial

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In the main function first, we created clientOptions with MongoDB URL and credentials and pass it to mongo.Connect function, Once connected we can check our connection by client.Ping function.

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The following code will use booksCollection variable to query the books collection from testdb.

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booksCollection := client.Database("testdb").Collection("books")
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Insert Documents

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First Let's create a Book struct to insert into the collection, in below code we are using collection.InsertOne function to insert a single document in the collection

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// Insert One document\nbook1 := Book{"Animal Farm", "George Orwell", "0451526341", "Signet Classics", 100}\ninsertResult, err := booksCollection.InsertOne(context.TODO(), book1)\nif err != nil {\n    log.Fatal(err)\n}\n\nfmt.Println("Inserted a single document: ", insertResult.InsertedID)
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To insert multiple documents at once we need to create a slice of Book object and pass it to collection.InsertMany

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// Insert multiple documents\nbook2 := Book{"Super Freakonomics", "Steven D. Levitt", "0062312871", "HARPER COLLINS USA", 100}\nbook3 := Book{"The Alchemist", "Paulo Coelho", "0062315005", "HarperOne", 100}\nmultipleBooks := []interface{}{book2, book3}\n\ninsertManyResult, err := booksCollection.InsertMany(context.TODO(), multipleBooks)\nif err != nil {\n    log.Fatal(err)\n}\n\nfmt.Println("Inserted multiple documents: ", insertManyResult.InsertedIDs)
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Update Documents

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We can update a single document by function collection.UpdateOne. It requires a filter document to match documents in the collection and an updated document to describe the update operation. You can build these using bson.D types. The below code will match the book with ISBN 0451526341 and increment the copies field by 10

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//Update one document\nfilter := bson.D{{"isbn", "0451526341"}}\n\nupdate := bson.D{\n    {"$inc", bson.D{\n        {"copies", 10},\n    }},\n}\n\nupdateResult, err := booksCollection.UpdateOne(context.TODO(), filter, update)\nif err != nil {\n    log.Fatal(err)\n}\n\nfmt.Printf("Matched %v documents and updated %v documents.\\n", updateResult.MatchedCount, updateResult.ModifiedCount)
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You can also update more than one documents at once in a single collection by function collection.UpdateMany, In it, we need to pass filter document and update document same as collection.UpdateOne

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Find Documents

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To find a single document, we can use function collection.FindOne(), we will pass a filter document and decode the result in the Book type variable

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// A variable in which result will be decoded\nvar result Book\n\nerr = booksCollection.FindOne(context.TODO(), filter).Decode(&result)\nif err != nil {\n    log.Fatal(err)\n}\n\nfmt.Printf("Found a single document: %+v\\n", result)
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To find multiple documents, we use function collection.Find(). This method returns a Cursor, It provides a stream of documents on which we can iterate or we can get all the docs by function cursor.All() in a slice of Book type.

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cursor, err := booksCollection.Find(context.TODO(), bson.D{{}})\nif err != nil {\n  log.Fatal(err)\n}\nvar books []Book\nif err = cursor.All(context.TODO(), &books); err != nil {\n  log.Fatal(err)\n}\nfmt.Printf("Found multiple documents: %+v\\n", books)
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Delete Documents

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We can delete documents from a collection using functions collection.DeleteOne() or collection.DeleteMany(). Here you pass bson.D{{}} as the filter argument, which will match all documents in the collection.

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deleteCollection, err := booksCollection.DeleteMany(context.TODO(), bson.D{{}})\nif err != nil {\n    log.Fatal(err)\n}\nfmt.Printf("Deleted %v documents in the books collection\\n", deleteCollection.DeletedCount)
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Entire collection can be dropped using the collection.Drop() function, it will remove all documents and metadata, such as indexes from the collection

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Once you have done all the operation, don't forget to close the MongoDB connection

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err = client.Disconnect(context.TODO())\n\nif err != nil {\n    log.Fatal(err)\n}\n\nfmt.Println("Connection to MongoDB closed.")
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Now you can easily use MongoDB as Datasource in your go application, You can found the complete code used in this tutorial on our Github Repo

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