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Learning Go From Hello
World to Web Service
Eric Potter

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Learning Go From Hello
World to Web Service
Eric Potter

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Background
Before we go
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Creators
Rob Pike
• Worked at Bell
Labs and Google
• co-creator of
UTF-8
Ken Thompson
• Designed and
implemented the
original Unix
Robert Griesemer
• Worked on
Google's V8
JavaScript engine
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Fast
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Tools
All systems go
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Installation
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Go CLI
• go run
• go build
• go mod init
• go test
• go get
• go fmt
• etc
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IDEs
VS Code GoLand ($)
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Hello World
Demo
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Hello World
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Types
Go your own way
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Basic Types
• bool
• string
• int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64
• rune // alias for int32 that represents a Unicode code point
• float32, float64
• complex64, complex128
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Variable Declaration
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Syntax
Let it go
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Terse
; ( )
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Notable Omissions
++i
do {}
while
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Function Syntax
C#
public <returnType> <name> (<args>)
Go
func <name> (<args>) <returnType>
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Fizz Buzz
Demo
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Fizz Buzz
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Questions
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Exercise 1
Euler 1
1) If we list all the natural numbers below 10 that are multiples of 3
or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.
2) The Math.Sin values for 2 is positive and the value for 5 is
negative. Print the sum of the positive sine values from the input
between 0 and 10.
If you get done, try Euler 2 (https://projecteuler.net/problem=2)
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Euler 1
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Arrays
Go home
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Declaring Arrays
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Accessing Array Elements
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Iterate over an Array
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The size is part of the type
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Slices
Go home
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Dynamic Sizing
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Ranges
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Classes
Go home
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Classes
Go home
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Packages & Structs

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Defining a Struct
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Associating Functions with Structs
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Interfaces
Go home
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Defining an Interface
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Questions
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Exercise 2
Create a GIF
Using the image/gif and image/color packages, create a gif of a
checker board.
Using the same libraries, create an animated gif of a sine wave.
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Concurrency
You go your way,
I’ll go mine
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Concurrent Functions
Demo
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Channels
Go change the
channel
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TextEntryWithTimeout
Demo
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TextEntryWithTimeout
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WaitGroups
Go wait in the corner
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Questions
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Exercise 3
Create a GIF Concurrently
Modify your code that creates a sine wave gif to create the file
concurrently while the user enters the output file name.
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Web Services
Go on
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net/http Package
• The core functionality is in a standard library.
• There are packages like gin that provide structure.
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net/http
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Data Access
Go get it
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database/sql
• Go uses a driver and plugin model.
• There are larger frameworks like Gorm
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database/sql
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Questions
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Exercise 4
Web Services
Create a webservice that returns the sine of a given number.
Create a webservice that returns your sine wave GIF
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Thank you
Eric Potter • @pottereric •
HumbleToolsmith.com
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