I finished reading Practical Go Language, so I’d like to leave some reading notes.

Having worked with Go for several years, I realized many things I didn’t know or had forgotten, making it a very educational experience.

Variable Names

• The suffix for variable names of types that satisfy the Error interface is Error
  • ex. NotImplementedError
• The prefix for variable names declared with errors.New is Err
  • ex. ErrNotImplemented := errors.New("Not Implemented!")
• While short forms of variable names are preferred, descriptive variable names are desirable for variables that will be used far from their declaration.
• Short forms of variable names should be used actively.
  • It’s acceptable to use var if you want to make the type explicit.

Package Names

• Packages named internal are not exposed outside the module (i.e., they cannot be used from packages other than the one containing internal and its sub-packages).
• Avoid duplication of package names and function names.
  • ○http.Server　✕http.HTTPServer
  • ○zip.NewWriter ✕zip.NewZipWriter
• Folders named ., _, and testdata are excluded from compilation.

Interface Names

• In standard packages, interfaces that have only a single method often have the suffix er.
  • ex. io.Reader, fmt.Stringer

Constants

• const can only be used for immutable values determined at compile time.
• Be cautious of unintended shifts in constant values with iota.
  • If there’s a possibility of adding constants other than at the end, define each constant individually instead of using iota.
  • Avoid using iota for values that will be used in other processes, not just one.
    • ex. Be careful with values returned to clients in HTTP server responses.
• To convert iota integer values to strings in logs, you can use golang.org/x/tools/cmd/stringer.
  • This is convenient when you need to avoid the hassle of deciphering integer values.

Data Masking

• This can be achieved by extending the Stringer and GoStringer interfaces.

Structs

• Struct embedding ≠ inheritance.
  • Inheritance represents a relationship where the child depends on the parent, while struct embedding represents a looser dependency of the parent on the child (this might be misleading). It’s not Is-A, but Has-A.
  • It’s delegation, not inheritance.
• If you want to distinguish a field from its zero value and use omitempty, use pointer types for the field.

Functions

• Places where it’s acceptable to use log.Fatal and panic:
  • main function, init function, functions with the Must prefix, and other application initialization processes.

Testing

• Detection of order dependence:
  • The test execution order is shuffled with go test -shuffle=on.