my-go-examples

my-go-examples

A place to keep my go code snippets and examples.

These go examples also contain information I gathered from other sources.

Table of Contents,

• API
• BASIC PROGRAMMING
• BASIC SYNTAX
  • Data Types
  • Functions
  • Interfaces
  • Methods
• BLOCKCHAIN
• CGO
• CLOUD SERVICES
• CRYPTOGRAPHY
  • ASYMMETRIC CRYPTOGRAPHY
  • HASHING
  • SYMMETRIC CRYPTOGRAPHY
• DATABASE
• DISTRIBUTED SYSTEMS
• GOROUTINES
• JEFFS GO TEMPLATES
• MESSAGING
• PACKAGES
• SINGLE BOARD COMPUTERS
• TESTING
• WEBSERVER

Documentation and reference,

• go-cheat-sheet
• my-go-packages
• my-go-tools

GitHub Webpage built with concourse ci

GO EXAMPLES

All sections in alphabetical order.

API

• http-GET-POST

  Using the standard net/http package to http.Get and http.PostForm.

• OAuth-2.0-google-cloud-storage-api (Under construction - check back soon)

  Using OAuth 2.0 to access a users google cloud storage (based on scopes) via googles api.

• OAuth-2.0-google-cloud-storage-api-over-NATS (Under construction - check back soon)

  Using OAuth 2.0 (frontend and backend via protobuf over NATS) to access a users google cloud storage (based on scopes) via googles api.

• simple-tcp-ip-server

  Using the standard net package to build a simple tcp server to handle requests concurrently over ip (tcp/ip).

• simple-webserver-with-REST

  Adding REST (GET, POST, PUT, DELETE) JSON API to my simple-webserver. See example below.

BASIC PROGRAMMING

Just cool programs that are very useful and can be used as building blocks for other cool programs.

• json

  Encode a struct to json and decode back to a struct.

• read-file

  Reading a file a few different ways.

• singly-linked-list

  A singly linked list (i.e. using just a head pointer).

BASIC SYNTAX

• DATA TYPES

  • closure

    An example of closure (a function that references variables from outside its body).

  • pointers1

    A struct passed to function by value (copy) and by address (reference).

  • pointers2

    An int passed to function by address (reference) and by int pointer (reference).

  • slices-underlying-array

    A slice being appended to showing the underlying array being added to the slice.

• FUNCTIONS

  • callback

    Passing a function (as an argument) to a function. Not really used that often.

  • recursion

    A function calling itself to make a fibonacci series.

  • shapes-using-functions

    Calculating the area and perimeter of circles, rectangles and triangles using functions. Also refer to method and interface implementations below.

• INTERFACES

  • interface

    A simple example of an interface as parameter and an interface as a return. Also see the next example that uses this in a package.

  • interface-package

    The same example as above but the interface and methods placed in a package.

  • interfaces-card-atm-bank

    Using interfaces to show how a bank card is used to interact with an atm and bank.

  • shapes-using-interfaces

    Calculating the area and perimeter of circles, rectangles and triangles using interfaces. Also refer to function and method implementations.

• METHODS

  • shapes-using-methods

    Calculating the area and perimeter of circles, rectangles and triangles using methods. Also refer to function and interface implementations above.

BLOCKCHAIN

• bitcoin-ledger

  Demonstrates the bitcoin ledger in a blockchain using the unspent transaction output model.

• create-bitcoin-address-from-ecdsa-publickey

  Create a bitcoin address from your ecdsa public key using the crypto/ecdsa standard package.

• jeffCoin Links to another repo

  I made a working cryptocurrency. This link will take you to that repo.

• single-node-blockchain-with-REST

  A simple single node sha256 blockchain with a REST JSON API (to view (GET) the blockchain and add (POST) a block).

CGO

Using c with go.

• simple-c-code

  A very simple example to show you how to write a c function in go.

• simple-c-code-using-stdio

  Same code from above, but using stdio.h for printf.

CLOUD SERVICES

• amazon-aws (Under construction - check back soon)

  Interacting with amazon's aws using aws-sdk-go client libraries.

• google-gcp

  Interacting with google's gcp using google-cloud-go client libraries.

CRYPTOGRAPHY

• ASYMMETRIC CRYPTOGRAPHY

  Great for digital signatures (verify sender) and receiving encrypted data.

  • ecdsa-digital-signature

    To verify who a message is from, create and verify a digital signature using the crypto/ecdsa standard package.

  • rsa-asymmetric-cryptography

    Encrypt a message using a public key. Decrypt the message using a private key. Key pair generated using the crypto/rsa standard package (RSA is a cryptosystem for public key encryption).

  • rsa-asymmetric-cryptography-with-digital-signature

    Using the above example, lets verify who the message is from. Create and verify a digital signature using the crypto/rsa standard package.

• HASHING

  Great for getting fingerprints.

  • bcrypt-password-hashing

    Store your password hash, not your password. Set your password hash and then check your password using bcrypt.

  • md5-hash-from-file

    Get an md5 hash (fingerprint) from an input file using the standard crypto/md5 package. I also added a flag to read in your .ssh/id_rsa.pub key to get your ssh fingerprint. Your github uses this for verification.

  • sha256-hash-from-file

    Get an sha256 hash (fingerprint) from an input file using the standard crypto/sha256 package.

• SYMMETRIC CRYPTOGRAPHY

  Using the same key to encrypt and decrypt.

  • aes-256

    AES-256 No Mode can only encrypt/decrypt 16 bytes of data.

  • aes-256-cbc

    AES-256 CBC (Cipher Block Chaining) mode where a block of plaintext is XORed with the previous cipherText block before being encrypted.

  • aes-256-cfb

    AES-256 CFB (Cipher FeedBack) mode is almost identical to CBC mode but performed in reverse.

  • aes-256-ctr

    AES-256 CTR (Counter) mode has similar characteristics to OFB, but also allows a random access property during decryption.

  • aes-256-gcm I like this one

    AES-256 GCM (Galois/Counter Mode) is a block cipher counter mode with authentication.

  • aes-256-ofb

    AES-256 OFB (Output FeedBack) mode makes a block cipher into a synchronous stream cipher. It generates keystream blocks, which are XORed with the plaintext blocks to get the cipherText.

DATABASE

• postgreSQL

  A relational database - Read/Write from/to a table.

• redis

  A non-relational (NoSQL) database - Set/Get from/to a key/value pair.

DISTRIBUTED SYSTEMS

• raft-consensus-algorithm

  A simple example of distributed consensus using Hashicorp raft, an asymmetric consensus algorithm where an elected leader issues commands to its followers.

GOROUTINES

Go is written for concurrency. The go runtime schedules goroutines on threads. The OS schedules these threads on cpus/cores.

• goroutines-async-channel-receive-no-waiting

  A goroutine asynchronously sending data (via a channel buffer) and a goroutine receiving that data, using the latest (if available) and does not wait.

• goroutines-async-channel-send-receive-waiting

  Sending data to a goroutine via an async channel. Both SEND and RCV will block/wait for data.

• goroutines-multi-core

  Concurrency across multiples cores. You can play around with workers, threads, cpus/cores and nice to find the fastest performance. It will find the total amount of prime numbers up to a number.

• goroutines-waitgroup

  Concurrency using a waitgroup (waiting for a collection of goroutines to finish).

• goroutines-worker-pools

  Concurrency using worker pools.

JEFFS GO TEMPLATES

My starting point for all my go projects.

• jeffs-basic-go-template

  A simple go template with flags, logging & error handling.

MESSAGING

• protobuf

  Using protobuf to show data -> marshal -> snd -> rcv -> unmarshal -> data.

• protobuf-NATS-publish-subscribe

  Using NATS (publish/subscribe) as a pipe to send protobuf messages. This is a model for one-to-many communication.

• protobuf-NATS-queue-groups

  Using NATS (queue groups) as a pipe to send protobuf messages. This is a model for one-to-one communication.

• protobuf-NATS-queue-groups-request-reply I like this one

  Using NATS (queue groups) as a pipe to send protobuf messages with a request and getting a reply back from the subscriber. This is a model for one-to-one communication.

• protobuf-NATS-request-reply

  Using NATS (request/reply) as a pipe to send protobuf messages. This is a model for a subscriber sending a msg with a request and getting a reply back from a subscriber. This is also a model for one-to-many communication.

• protobuf-NATS-request-reply-goroutines

  Same as above protobuf-NATS-request-reply but using goroutines for subscribers. This is also a model for one-to-one communication.

PACKAGES

Refer to my repo my-go-packages for packages I created. Refer to golang.org/pkg for the standard go packages

• errors (github.com/pkg/errors)

  Error Handling using non-standard github.com/pkg/errors package.

• flag (standard)

  The flag package makes it easy to implement command-line flag parsing.

• fmt-scan (standard)

  The fmt package makes it easy to scan user input using fmt.Scan() by reading os.Stdin.

• logrus (github.com/sirupsen/logrus)

  Logging using non-standard logrus package.

• net/http (standard)

  See above http-GET-POST and below simple-webserver examples.

• test-jeffshapes (github.com/JeffDeCola/my-go-packages/jeffshapes)

  Testing the jeffshapes package (below).

SINGLE BOARD COMPUTERS

• raspi-gpio

  Using googles periph (peripherals in go) library to control a Raspberry Pi's GPIO (General Purpose Input/Output) pins. The example used will be turning on/off an external LED via a button.

TESTING

• gomock

  Using gomock on an interface and using the go tool gotests for unit testing.

• gotests

  Using the go tool gotests to test a very simple function and method.

• gotests-complex-function

  Using the go tool gotests to test a function with complex inputs and outputs.

WEBSERVER

• simple-webserver

  Using the standard net/http package to build a simple webserver. I added a REST JSON API to this example in the above example simple-webserver-with-REST.

• simple-webserver-with-reactJS

  Adding ReactJS, an open source UI, to to create a single-page App (SPA) (Allowing content to be dynamically displayed without requiring you to refresh or navigate to a different page).