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05-write-your-first-library-package/printer-exercise/exercise.md

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+# EXERCISE
+1. Create a new library
+2. In it, create a function that returns Go version
+3. Create a command and import your library
+4. Call your function that returns Go version
+5. Run your program
+
+## HINTS
+**Create your package function like this:**
+
+```go
+func Version() string {
+    return runtime.Version()
+}
+```
+
+## EXPECTED OUTPUT
+It should print the current Go version on your system.

05-write-your-first-library-package/printer-exercise/questions.md

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+## Which one below is correct?
+**NOTE** _There are explanations inside the answers. Even if you know the answer please try to select all of them one by one, so you can read the explanations._
+
+1. You can run a library package.
+2. In a library package there should be a function named main (func main).
+3. You can compile a library package. *CORRECT*
+4. You have to compile a library package.
+
+> 1. You can't, but you can import it from other packages.
+> 2. In a library package, you don't have to include a main function. Because, it isn't an executable package. Only in executable packages you need a main func.
+> 4. You don't have to compile it. When you import it, it will automatically be built by the other program or library when it gets compiled or ran.
+
+
+## What do you need to export a name?
+1. You need to type it in all capital letters
+2. You need to type its first letter as a capital letter *CORRECT*
+3. You need to put it inside a function scope
+4. You need to create a new file for that name
+
+> 1. When you do so, it will be exported, that's true, but don't do that; so I assume that this answer is not correct :)
+> 2. That's right. Then the other packages can access it.
+> 3. It should be in a package scope, not function scope.
+> 4. You don't have to do that.
+
+
+## How can you use a function from your library from an executable program?
+1. You need to export your library package first; then you can access to its imported names
+2. You need to import your library package first; then you can access to its exported names *CORRECT*
+3. You can access your library package as if it's in your executable program
+4. You can import it just by using its name
+
+> 1. You can't export packages. All packages are already exported. Unless you put them in a directory called: "internal". But, that's an advanced topic for now.
+> 2. That's right.
+> 3. You can't access to a package from another package without importing it.
+> 4. No, you can't. You need to import it using its full directory path after GOPATH. BTW, in the near future this may change with the Go modules support.
+
+
+## In the following program, which names are exported?
+```go
+package wizard
+
+import "fmt"
+
+func doMagic() {
+    fmt.Println("enchanted!")
+}
+
+func Fireball() {
+    fmt.Println("fireball!!!")
+}
+```
+
+1. fmt
+2. doMagic
+3. Fireball *CORRECT*
+4. Println
+
+> 1. That's just an imported package name.
+> 2. It starts with a lowercase letter; so, it's not exported.
+> 3. That's right. It starts with a capital letter.
+> 4. This isn't your function. It's already been exported in the fmt package. But, it isn't exported here.
+
+
+## In the following program, which names are exported?
+```go
+package wizard
+import "fmt"
+
+var one string
+var Two string
+var greenTrees string
+
+func doMagic() {
+    fmt.Println("enchanted!")
+}
+
+func Fireball() {
+    fmt.Println("fireball!!!")
+}
+```
+
+1. doMagic and Fireball
+2. Fireball and Two *CORRECT*
+3. Fireball, greenTrees and Two
+4. Fireball, greenTrees, one and Two
+
+> 1. doMagic starts with a lowercase letter; so, it's not exported.
+> 2. That's right. Fireball and Two, they both start with a capital letter.
+> 3. greenTrees starts with a lowercase letter; so, it's not exported.
+> 4. one and greenTrees do not start with capital letters; so, they're not exported.

05-write-your-first-library-package/printer-exercise/solution/golang/cmd/main.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt" // You should replace this with your username
+
+	"github.com/inancgumus/learngo/05-write-your-first-library-package/printer-exercise/solution/golang"
+)
+
+func main() {
+	fmt.Println(golang.Version())
+}

05-write-your-first-library-package/printer-exercise/solution/golang/go.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package golang
+
+import (
+	"runtime"
+)
+
+// Version returns the current Go version
+func Version() string {
+	return runtime.Version()
+}

05-write-your-first-library-package/printer/cmd/main.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+// Automatically imports!... AWESOME!
+import "github.com/inancgumus/learngo/05-write-your-first-library-package/printer"
+
+func main() {
+	printer.Hello()
+}

05-write-your-first-library-package/printer/printer.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package printer
+
+import "fmt"
+
+// Hello is an exported function
+func Hello() {
+	fmt.Println("exported hello")
+}