added lexical demo

concurrency/confinement/lexical/main.go

@@ -0,0 +1,45 @@
+package main
+
+import "fmt"
+
+// Confinement is the simple yet powerful idea of ensuring information is only ever available from one concurrent process.
+// There are two kinds of confinement possible: ad hoc and lexical.
+
+// Lexical confinement involves using lexical scope to expose only the correct data and
+// concurrency primitives for multiple concurrent processes to use. It makes it impossible to do the wrong thing.
+
+func main() {
+	lexicalDemo()
+}
+
+func lexicalDemo() {
+	// Here we instantiate the channel within the lexical scope of the chanOwner function.
+	// This limits the scope of the write aspect of the results channel to the closure
+	// defined below it. In other words, it confines the write aspect of this channel to
+	// prevent other goroutines from writing to it.
+	chanOwner := func() <-chan int {
+		results := make(chan int, 5)
+		go func() {
+			defer close(results)
+			for i := 0; i <= 5; i++ {
+				results <- i
+			}
+		}()
+		return results
+	}
+
+	// Here we receive a read-only copy of an int channel. By declaring that the only
+	// usage we require is read access, we confine usage of the channel within the consume function to only reads
+	comsumer := func(results <-chan int) {
+		for result := range results {
+			fmt.Println("Received: %d\n", result)
+		}
+		fmt.Println("Done Receiving!")
+	}
+
+	// Here we receive the read aspect of the channel and we’re able to pass it into the
+	// consumer, which can do nothing but read from it. Once again this confines the
+	// main goroutine to a read-only view of the channel.
+	results := chanOwner()
+	comsumer(results)
+}

interface-semantics/main.go

@@ -0,0 +1,36 @@
+package main
+
+import "fmt"
+
+// interface in Go provides both a value and pointer semantic form.
+// An interface can store its own copy of a value (value semantics), or a value can be shared
+// with the interface by storing a copy of the value’s address (pointer semantics).
+// This is where the value/pointer semantics come in for interfaces
+
+type printer interface {
+	print()
+}
+
+type user struct {
+	name string
+}
+
+func (u user) print() {
+	fmt.Println("User Name:", u.name)
+}
+
+func main() {
+	u := user{"Bill"}
+	entities := []printer{
+		u,
+		&u,
+	}
+	u.name = "Bill_CHG"
+	for _, e := range entities {
+		e.print()
+	}
+}
+
+func ptest(p printer) {
+	p.print()
+}