How do you handle HTTP server health checks in Go?

package main

import (
	"fmt"
	"net/http"
)

func main() {
	http.HandleFunc("/health", healthHandler)
	http.ListenAndServe(":8080", nil)
}

func healthHandler(w http.ResponseWriter, r *http.Request) {
	// Check the health of the server and return a status code accordingly
	if serverIsHealthy() {
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, "Server is healthy")
	} else {
		w.WriteHeader(http.StatusInternalServerError)
		fmt.Fprint(w, "Server is not healthy")
	}
}

func serverIsHealthy() bool {
	// Check the health of the server and return true or false accordingly
	// For example, check if the server can connect to the database
	return true
}

In this example, we create an HTTP server and define a /health endpoint that calls the healthHandler function when it receives a request. The healthHandler function checks the health of the server by calling the serverIsHealthy function and returns a status code and a message indicating whether the server is healthy or not.

The serverIsHealthy function checks the health of the server by performing whatever checks are necessary. For example, it might check if the server can connect to a database, if all the required services are running, or if there are any pending tasks that need to be completed.

The health check endpoint can be used by external monitoring tools to check if the server is healthy. For example, Kubernetes can use this endpoint to determine if a pod is ready to receive traffic.

In Go, there are many third-party packages available that can help you implement HTTP server health checks. One popular package is github.com/heptiolabs/healthcheck.

Here's an example of how to use this package to implement a health check endpoint in your HTTP server:

package main

import (
	"net/http"

	"github.com/heptiolabs/healthcheck"
)

func main() {
	// Create a new health check handler
	h := healthcheck.NewHandler()

	// Register health checks for any dependencies
	h.AddLivenessCheck("database", healthcheck.DatabasePingCheck("mysql", "user:password@tcp(db:3306)/mydatabase"))

	// Create an HTTP server and add the health check handler as a handler
	http.HandleFunc("/health", h.Handler)
	http.ListenAndServe(":8080", nil)
}

In this example, we create a new healthcheck.Handler and add a liveness check for a MySQL database using the DatabasePingCheck function. This check will return a 200 OK status code if the database can be pinged successfully.

You can add additional health checks for other dependencies, such as cache servers or message queues, using the AddLivenessCheck or AddReadinessCheck methods.

Finally, we add the health check handler to our HTTP server using http.HandleFunc and start the server using http.ListenAndServe. Now, when you make a request to the /health endpoint, you will get a JSON response containing the status of all registered health checks.