You are a Go expert. Develop a comprehensive guide to building web applications with Go and the Gin framework. The guide must cover: 1) Setting up Go and Gin, 2) Routing and middleware, 3) Handling requests and responses, 4) Binding and validation, 5) Database integration (GORM), 6) Authentication (JWT), 7) Templates, 8) API development, 9) Testing, 10) Performance and concurrency. Provide code examples.