work on chapter 09

learning_go/09_modules_packages_imports/Makefile

@@ -0,0 +1,21 @@
+.DEFAULT_GOAL := run
+
+fmt:
+	go fmt ./...
+.PHONY: fmt
+
+lint: fmt
+	golint ./...
+.PHONY: lint
+
+vet: fmt
+	go vet ./...
+.PHONY: vet
+
+build: vet
+	go build rand_and_crand.go
+.PHONY: build
+
+run: vet
+	go run rand_and_crand.go
+.PHONY: run

learning_go/09_modules_packages_imports/README.md

@@ -16,3 +16,13 @@
     - version of dependencies
     - (optional) replace 
     - (optional) exclude
+* `pkg` (for actual code) and `cmd` (for executables)
+
+### Packages
+* `Capitalized` names are exported
+* `interal` package is only available to packages directly above it and it's subpackages
+
+### API
+* `alias` is different name for `type` (basically)
+
+### Imports

learning_go/09_modules_packages_imports/go.mod

@@ -0,0 +1,3 @@
+module main
+
+go 1.20

learning_go/09_modules_packages_imports/rand_and_crand.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	crand "crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+)
+
+func main() {
+	r := seedRand()
+	fmt.Println(r.Int())
+}
+
+func seedRand() *rand.Rand {
+	var b [8]byte
+	_, err := crand.Read(b[:])
+	if err != nil {
+		panic("cannot seed with cryptographic random number generator")
+	}
+	r := rand.New(rand.NewSource(int64(binary.LittleEndian.Uint64(b[:]))))
+	return r
+}