Best practice struct configuration pattern for Golang

[japananh]

Best practice struct configuration pattern for Golang

• Reference: https://www.youtube.com/watch?v=MDy7JQN5MN4

Before

package main

type Server struct {
    maxConn int
    id              string
    tls             bool
}

// Problem: Parameter will grow when we need more configs
func newServer(maxConn int, id string, tls bool) *Server {
    return &Server{
        maxConn: maxConn,
        id:              id,
        tls:             tls,
}

func main() {
    s := NewServer(20, "id", false)
    
    fmt.Printf("%+v\n", s)
}

After

package main

type OptFunc func(*Opts)

type Opts struct {
    maxConn int
    id              string
    tls             bool
}

func defaultOpts() Opts {
    return Opts{
        maxConn: 10, 
        id:              "default",
        tls:             false,
    }
}

func withTLS(opts *Opts) {
    opts.tls = true
}

func withMaxConn(n int) OptFun {
    return func(opts *Opts) {
        opts.maxConn = n
    }
}

type Server struct {
    Opts
}

func NewServer(opts ...OptFunc) *Server {
    o := defailtOpts()

    for _, fn := range opts {
        fn(&o)
    }

    return &Server{
        Opts: o,
    }
}

func main() {
    s := NewServer(withTLS, withMaxConn(20))
    
    fmt.Printf("%+v\n", s)
}