Added sections on go context and flags

docs/go/advanced/context.md

@@ -0,0 +1,41 @@
+# Context
+
+Context is a way of passing information or enforcing timeouts when calling functions throughout your application as a single requests goes from layer to layer. This is usually passed as the first parameter in your functions if being used.
+
+```go
+// create an empty context
+ctx := context.Background()
+
+// append value to context
+ctx = context.WithValue(ctx, "key", "value")
+
+value := ctx.Value("key")
+```
+
+## Timeouts
+
+```go
+ctx, cancel := context.WithTimeout(context.Background(), 2 * time.Second)
+
+defer cancel() // can call before timeout
+go longRunningFunc(ctx)
+
+select {
+case <-ctx.Done():
+    fms.Println("done blocking main thread also!")
+}
+time.Sleep(2*time.Second)
+
+func longRunningFunc(ctx context.Context) {
+    for {
+        select {
+        case <-ctx.Done():
+            fmt.Println("timed out")
+            return
+        default:
+            fmt.Println("still processing")
+        }
+        time.Sleep(1*time.Second)
+    }
+}
+```

docs/go/advanced/flags.md

@@ -0,0 +1,62 @@
+# Flags
+
+Flags allow you to define command line arguments to your applications. This gives you some more useful features over `os.Args` such as help strings and validation.
+
+```go
+var age = flag.Int("age", 20, "age of user") // arg name, default, help
+fmt.Println(*age) // gives us a pointer to the value
+// or
+var age int
+flag.IntVar(&age, "age", 20, "age of user")
+fmt.Println(age)
+
+// with structs
+type ServerConfig struct {
+    port int
+    env string
+}
+
+var config ServerConfig
+flag.IntVar(&config.port, "port", 8000, "server port")
+flag.StringVar(&config.env, "env", "dev", "environment")
+flag.Parse()
+```
+
+## Custom Flags
+
+Normally flags can only be strings, ints, or booleans, but you can create your own custom flag types by implementing the `Value` interface which has two functions, `String` and `Set`.
+
+```go
+type AddrVal struct {
+    addr *string
+}
+
+func (a AddrVal) String() string {
+    if a.addr == nil {
+        return ""
+    }
+    return *a.addr
+}
+
+func (a AddrVal) Set(s string) error {
+    if err := validateAddr(s); err != nil {
+        return err
+    }
+    *a.addr = s
+    return nil
+}
+
+func validateAddr(addr string) error {
+    // validate address
+    return nil
+}
+
+func main() {
+    addr := ":8080" // default value
+    flag.Var(AddrVal{&addr}, "addr", "address to listen on")
+    flag.Parse()
+
+    fmt.Println("address: ", addr)
+}
+
+```

docs/go/advanced/http.md

@@ -10,6 +10,8 @@ go get github.com/go-chi/chi/v5/middleware
 go get github.com/go-chi/cors
 ```
 
+## Basic Implementation
+
 ```go
 // main.go
 package main
@@ -241,6 +243,16 @@ func (app *Config) errorJSON(w http.ResponseWriter, err error, status ...int) er
 }
 ```
 
+## Adding Custom Types to Session
+
+```go
+// main.go, before creating session
+gob.Register(data.User{})
+
+// to add type to session
+app.Session.Put(r.Context(), "user", user) // user *data.User
+```
+
 ## Testing
 
 ```go

docs/go/sidebar.json

@@ -16,6 +16,8 @@
   {
     "text": "Go Advanced",
     "items": [
+      {"text": "Context", "link": "/go/advanced/context"},
+      {"text": "Flags", "link": "/go/advanced/flags"},
       { "text": "Testing", "link": "/go/advanced/testing" },
       {"text": "HTTP", "link": "/go/advanced/http"},
       {"text": "RPC", "link": "/go/advanced/rpc"},