I’m working on integrating PostgreSQL into my Go project and have a few questions about structuring the psqlClient:

Initialization Strategy: Should I initialize the psqlClient at the start of the application and maintain a single instance throughout? If so, how do I ensure it’s globally accessible? But then opens up to posibility so many problems.

func main(){
    // global instance
    // problem: race conditions, and how to access from different services
    psqlClient = psql_client.NewPsqlClient()
}

Service Initialization: Alternatively, is it better to initialize the psqlClient at the time of service initialization? My concern here is that multiple project-level services (like role_service.go and action_service.go) might each need their own client, leading to potential duplication of connection pools and other resources.

---- psql_client.go ----
type PsqlClient{
    client *db.SQL // or something like this
}

func NewPsqlClient() PsqlClient{
    // initialize new psql client on each call
    return psqlClient
}


--- user_service.go ----
func NewUserService(){
    psqlClient = psql_client.NewPsqlClient() // psql client duplicated across service
}

---- action_service.go ----
func NewActionService(){
    psqlClient = psql_client.NewPsqlClient() // psql client duplicated across service
}

Using sync.Once for Singleton Initialization: I’ve considered using sync.Once to ensure only a single instance of psqlClient is created. However, I foresee a challenge: what if different services require initialization of psqlClient with different databases?

psql_client.go

var psqlClient psqlClient
var psqlClientOnce sync.Once
func NewPsqlClient() {
    psqlClientOnce.do(
        // logic to initialize psqlClient
        psqlClient = initializedClient
    )
}

Could anyone share insights or best practices on how to effectively manage psqlClient within a Go application? Also, by “service” I mean project-level services such as role_service.go and action_service.go. Thanks in advance for your help!