Readiness and liveness probes with dependency checks

                  package health

import (
  "context"
  "net"
  "net/http"
  "time"
)

type Checker interface {
  Ping(ctx context.Context) error
}

func Liveness(w http.ResponseWriter, _ *http.Request) {
  w.WriteHeader(http.StatusOK)
  _, _ = w.Write([]byte("ok"))
}

func Readiness(chk Checker) http.HandlerFunc {
  return func(w http.ResponseWriter, r *http.Request) {
    ctx, cancel := context.WithTimeout(r.Context(), 300*time.Millisecond)
    defer cancel()

    if err := chk.Ping(ctx); err != nil {
      w.WriteHeader(http.StatusServiceUnavailable)
      _, _ = w.Write([]byte("not_ready"))
      return
    }

    w.WriteHeader(http.StatusOK)
    _, _ = w.Write([]byte("ready"))
  }
}