1.
THE BEST FEATURE OF GO
A 5-YEAR RETROSPECTIVE

2.
GO & I
▸ Programming since the ‘90s
▸ Former C, C++, PHP, Python, JavaScript, Java programmer
▸ Switched to Go in 2012
▸ Handful of large Go implementations across 2 companies
▸ Have my own shortlist of favorite Go features over the years
▸ One of those features is exceptional

3.
NOTABLE FEATURES

4.
COMPILER & SYNTAX
▸ Avoids historically error prone constructs
▸ Highly assistive error messages
▸ Focus on intention rather than expression
▸ If it compiles, it mostly works
▸ Very high performance with low effort

5.
SMALL FEATURE SET
▸ A tad bigger than C
▸ Orthogonal, Minimal
▸ Easy to Learn
▸ Easy to Remember
▸ Minimized Personal Feature Subsets

6.
STANDARDIZED FORMATTING
▸ 10
x improvement in readability
▸ Improved collaboration between team members
▸ Improved collaboration across teams
▸ More easily accessible Open Source code

7.
SENSIBLE UNICODE & STRINGS
▸ UTF-8 encoded strings
▸ Compatible []byte and string memory layout
▸ Minimized copying between buffers and strings
▸ Rich set of string manipulators available

8.
GOROUTINES & CHANNELS
▸ Declarative Parallel Programming
▸ Based on CSP Principles
▸ Straight-forward procedural logic — no callback mess
▸ Any function/method can be invoked asynchronously

9.
SELECT STATEMENT
▸ Go’s tour de force in parallel programming
▸ Simple, declarative expression of event synchronization
▸ Makes previously complicated flows trivial to implement
▸ Timeouts
▸ Cancellation
▸ Back-pressure handling
▸ Combinations of the above

10.
CAPABILITY
GO CHANGED MY PROGRAMMING

11.
PERFORMANCE AND COMPLEXITY WITH CONFIDENCE
▸ First production system in Go: a Multiplayer Game Engine
▸ Made > $1000,000 in a year
▸ Also, a rate limiter, a reverse proxy, a micro-service simulator,
deployment orchestrator, cluster auto-scaler…
▸ … even a bespoke datastore!

12.
PROGRAMMER
ONE FEATURE CHANGED ME AS A

13.
THE BEST FEATURE OF GO
▸ Acts as a stand-in for the user
▸ Improves documentation
▸ Guides program design
▸ Aids Refactoring & Debugging
▸ Finds unnecessary/dysfunctional code
▸ Gives rapid feedback on performance characteristics
Can you guess what it is?

14.
GO TEST

15.
GO TEST IN DESIGN PHASE
USER SIMULATION
Use package pkg_test to get “3rd Party” view
▸ Allows accessing your package like an end-user
▸ Helps the provider switch mind to that of a consumer
▸ Helps in deciding exported symbols
▸ Improves API Design

16.
GO TEST IN DESIGN PHASE
DOCUMENTATION
▸ Write testable, runnable Examples that show up in the
documentation
▸ Document methods: func ExampleStruct_Method() {…}
▸ Document functions: func ExampleFunction() {…}
▸ Document use cases: func Example_useCase() {…}

17.
GO TEST IN DESIGN PHASE
PROGRAM DESIGN
▸ Monolithic do-it-all functions are hard to test
▸ The need to test improves modularity, functional cohesion
▸ Sample Strategy:
1. Implement business logic as native APIs with native data — test
entire business logic
2. Implement data load/store from native to database — test data
validation and access
3. Implement remoting (HTTP etc.) APIs — test request interpretation
and response serialization

18.
GO TEST IN IMPLEMENTATION PHASE
REFACTORING
▸ Table driven testing helps in basic I/O validation
▸ Top-level tests for checking various scenarios
▸ Subtests help in isolating granular functionality
▸ Non-compilable tests indicate changes in package interface
▸ Failing tests indicate changes in functional behaviours

19.
GO TEST IN IMPLEMENTATION PHASE
DEBUGGING
▸ Parallel tests with race detector for
unsafe concurrent data access
▸ Optional long running tests for
deeper verification
▸ Test cases can be complex enough
to act as simulators.
E.g. the graph here is from a 1-
million iteration sim of smartcb
Error Rate Learned Rate SmartCB Regular CB

20.
GO TEST IN IMPLEMENTATION PHASE
FINDING USELESS CODE
▸ $ go test -coverprofile to find which lines were executed
by the test
▸ Untouched lines =>
▸ The tests don’t check the logic for which the code is written,
or
▸ The code is untestable because it’s dead or represents a
logically impossible scenario

21.
GO TEST IN OPTIMIZATION PHASE
BENCHMARKING
▸ $ go test -bench to see how fast functions/methods are
▸ $ go test -bench -cpu to observe multi-core scalability
▸ $ go test -bench -cpuprofile to see what parts of the
code are slow
▸ $ go test -bench -memprofile to see what parts of the
code eat up memory
▸ Run go test -bench before every commit to find
performance regressions

22.
GO TEST IS LIKE A PROGRAMMER’S
ASSISTANT. AN IRONMAN’S JARVIS. A
BATMAN’S ALFRED.
IT HAPPENS TO RUN UNIT TESTS TOO
Yours Truly
MORE THAN UNIT TESTING

23.
THANK YOU
TAHIR HASHMI, PT TOKOPEDIA, JAN 2018

24.
FURTHER INFORMATION
▸ talks.golang.org
▸ tour.golang.org
▸ tech.t9i.in
▸ @code_martial