An example Google Firebase Firestore client in Golang, with Create/Update/Read. ** Update the service_account.json file and project-id to yours before running.

firebase-firestore.go

package main

import (
   "context"
   "encoding/json"
   "fmt"
   "log"

   "cloud.google.com/go/firestore"
   "google.golang.org/api/option"
)

func main() {
   ctx := context.Background()
   opt := option.WithCredentialsFile("../../service_account.json")
   client, err := firestore.NewClient(ctx, "tiebing-test1", opt)
   if err != nil {
        log.Fatalf("firestore new error:%s\n", err)
   }
   defer client.Close()

   //create
   if false {
        wr, err := client.Doc("States/Colorado").Create(ctx, map[string]interface{}{
                "capital": "Denver",
                "pop":     5.5,
        })
        if err != nil {
                log.Fatalf("firestore Doc Create error:%s\n", err)
        }
        fmt.Println(wr.UpdateTime)
   }

   //update
   if true {
        if _, err := client.Doc("States/Colorado").
                Update(context.Background(), []firestore.Update{{"FlagColor", nil, "Red"}, {Path: "Location", Value: "Middle"}}); err != nil {
                log.Fatalf("Update error: %s\n", err)
        }
   }

   //read
   state, err := client.Doc("States/Colorado").Get(context.Background())
   json, err := json.MarshalIndent(state.Data(), "", "  ")
   fmt.Println(string(json))
   
    //event, specific collection
    col := client.Collection("States")
    iter := col.Snapshots(context.Background())
    defer iter.Stop()

    for {
        //Next() call blocks, until changes are received
        doc, err := iter.Next()
        if err != nil {
            if err == iterator.Done {
                break
            }
            //return err
            log.Printf("next iter error %s\n", err)
        }

        for _, change := range doc.Changes {
            // access the change.Doc returns the Document,
            // which contains Data() and DataTo(&p) methods.
            switch change.Kind {
            case firestore.DocumentAdded:
                log.Printf("doc added, %s\n", change.Doc.Ref.Path)
                // on added it returns the existing ones.
                isNew := change.Doc.CreateTime.After(l.startTime)
            case firestore.DocumentModified:
                log.Printf("doc modified, %s\n", change.Doc.Ref.Path)
            case firestore.DocumentRemoved:
                log.Printf("doc removed, %s\n", change.Doc.Ref.Path)
            }
        }

    }


}