Go Util

A repo for my Golang util libraries.

sync/successgroup

This package is the counter-part of golang.org/x/sync/errgroup.

Instead of returning when an error occurs, it instead returns immediately when there's a successful result. This can be used to issue the same request to several different sources and just use the first result.

Example

The following example will fire the same request to two different databases. This is an example of improved latency (min(dbPrimary, dbReadReplica)) and improved availability (dbPrimaryHealthy || dbReadReplicaHealthy).

group, ctx := successgroup.WithContext(context.Background())

for db := range []Database{dbPrimary, dbReadReplica} {
    group.Go(func() error {
        return db.GetUsersCount(ctx)
    })
}
userCountRaw, dbErr := group.Wait()
if dbErr != nil {
    panic(fmt.Sprintf("Database error: %s", dbErr.Error()))
}
userCount := userCountRaw.(int)
fmt.Println("Got user count:", userCount)