Response Headers in Go

HTTP responses include headers that carry metadata about the response. So far you have written response bodies and set status codes. In this Go Byte, you will learn how to set response headers, what they represent, and why the order of operations matters when writing a response. What You'll Learn: - What HTTP response headers are and where they fit in a response - How to set headers using the Header method on ResponseWriter - Why headers and status codes must be set before writing the body - How Content-Type and other headers help clients interpret your response Conceptual Explanation: An HTTP response has three parts: status code, headers, and body. Headers provide additional information such as Content-Type (how to interpret the body) and Cache-Control (caching behaviour). In Go, you use w.Header().Set to modify headers before they are sent. The first call that writes to the response body triggers Go to send the headers. Once sent, they cannot be changed. If you do not call WriteHeader, Go sends 200 OK automatically. Setting headers and status code before writing the body ensures your response is correct. How It Fits: Headers are essential for APIs and web servers. Clients need Content-Type to know how to parse your response. Caching headers affect performance. Understanding the order (headers, then status, then body) prevents subtle bugs and ensures your HTTP handlers behave correctly. This builds on writing response bodies and setting status codes. Key Takeaways: - Headers store metadata about a response and are sent before the body - Use w.Header().Set to modify response headers - Use w.WriteHeader to set the status code - Headers and status must be set before any write to the body - If no status is set, Go sends 200 OK by default Try the challenge from the video before checking the solution. Links: Lesson folder on GitHub: https://github.com/GaryClarke/go-bytes/tree/main/response-headers Build your first Go app with me: https://www.garyclarke.tech/p/build-your-first-go-app Join the mailing list for new lessons and resources: https://content.garyclarke.tech/go-bytes-signup Follow on X/Twitter: https://twitter.com/garyclarketech Connect on LinkedIn: https://www.linkedin.com/in/garyclarketech/ Subscribe for more Go lessons. #golang #go #programming #coding #learnprogramming #gobytes