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THE BEST FEATURE OF GO
A 5-YEAR RETROSPECTIVE
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
NOTABLE FEATURES
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
SMALL FEATURE SET
▸ A tad bigger than C
▸ Orthogonal, Minimal
▸ Easy to Learn
▸ Easy to Remember
▸ Minimized Personal Feature Subsets
STANDARDIZED FORMATTING
▸ 10
x improvement in readability
▸ Improved collaboration between team members
▸ Improved collaboration across teams
▸ More easily accessible Open Source code
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
GOROUTINES & CHANNELS
▸ Declarative Parallel Programming
▸ Based on CSP Principles
▸ Straight-forward procedural logic — no callback mess
▸ Any function/method can be invoked asynchronously
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
CAPABILITY
GO CHANGED MY PROGRAMMING
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!
PROGRAMMER
ONE FEATURE CHANGED ME AS A
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?
GO TEST
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
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() {…}
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
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
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
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
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
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
THANK YOU
TAHIR HASHMI, PT TOKOPEDIA, JAN 2018
FURTHER INFORMATION
▸ talks.golang.org
▸ tour.golang.org
▸ tech.t9i.in
▸ @code_martial

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The Best Feature of Go – A 5 Year Retrospective

  • 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
  • 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
  • 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!
  • 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?
  • 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