Add notes: GC, Interface, Error

Author: arvryna

Diff for: README.md

@@ -38,6 +38,7 @@ func(s string){fmt.print(s)}("Hello")
 NOTE: capturing the state means that, the closure will somehow associate that specific closure with the variables passed to it. In the above example, this specific instance of a function is linked with the variable passed to it. It becomes particularly important when enclosing closures in loops. So each instance of closure will be given a unique reference to variable s.
 
 # Pointers
+- Share memory by pointer
 - Map by default is reference in go
 - Passing pointer by reference example
 
@@ -80,6 +81,13 @@ fetch(&data)
 - If all goroutines are deadlocked, go raises panic to kill program, but if there is partial failure of go-routines, the program 
   continues to function but may behave uncertain.
 
+# Interface:
+- They define behaviour of an Object, by expecting presence of certain methods.
+- This helps us to implement OOP in go. 
+- passing interface as parameter provides a clean way to generalize and allow us to pass different kinds of 
+  objects
+- See example here:  https://github.com/arvryna/sled/blob/main/internal/service/task.go
+
 # Go Tools:
 > Detecting race conditions ?
 - Use race flag to detect race conditions in the program
@@ -100,6 +108,11 @@ signal.Notify(sigListen, syscall.SIGINT, syscall.SIGTERM)
 // Add code for graceful shutdown here
 ```
 
+# Interceptors
+Block of code that you want to execute before it executes a handler of web request for example. This works similar
+to constuct like before_action, after_action in rails for example. 
+
+
 # Working with docker
 An example of a simple hw app with a dockerfile can be found here `samples/greeter`
 
@@ -112,6 +125,3 @@ An example of a simple hw app with a dockerfile can be found here `samples/greet
 - [Google go's guide](https://github.com/golang/go/wiki/CodeReviewComments)
 - [Effective go](https://go.dev/doc/effective_go)
 - [Kubernets go coding convention](https://www.kubernetes.dev/docs/guide/coding-convention/)
-
-# Best practices:
-- Use defer whenever possible

Diff for: advanced/garbage-collection.md

@@ -0,0 +1,6 @@
+
+# Source code of Go's garbage collection here:
+https://github.com/golang/go/blob/master/src/runtime/mgc.go
+
+# Basics:
+- stack allocations are cleaned by themselves eg, function calls and its local vars (no need for GC)

Diff for: best-practices.md

@@ -0,0 +1,7 @@
+
+# Best practices:
+- Use defer whenever possible
+
+# Errors:
+- Export/Return error as variable, it helps you to compare error easily, instead of comparing strings.
+- Another way is to create a custom type to encapsulate message and defining error codes. 

Diff for: go-dep.md renamed to dependencies.md

@@ -7,4 +7,8 @@
 - can read config from remote systems like etcd, or consul
 - it can watch for config file changes and also notify the go-process
 - you can marshal/unmarshal using mapstructure
-- `go get github.com/spf13/viper`
+- `go get github.com/spf13/viper`
+
+# ORM
+- gorm is a popular ORM
+- to connect with postgres, driver is required additionally

Diff for: r.sh

@@ -0,0 +1,3 @@
+#! /bin/bash
+
+go run main.go