2.1 Names

The names of Go functions, variables, constants, types, statement labels, and packages follow a simple rule: a name begins with a letter (that is, anything that Unicode deems a letter) or an underscore and may have any number of additional letters, digits, and underscores. Case matters: heapSort and Heapsort are different names.

Go has 25 keywords like if and switch that may be used only where the syntax permits; they can’t be used as names.

Click here to view code image

break        default      func         interface    select
case         defer        go           map          struct
chan         else         goto         package      switch
const        fallthrough  if           range        type
continue     for          import       return       var

In addition, there are about three dozen predeclared names like int and true for built-in constants, types, and functions:

These names are not reserved, so you may use them in declarations. We’ll see a handful of places where redeclaring one of them makes sense, but beware of the potential for confusion.

If an entity is declared within a function, it is local to that function. If declared outside of a function, however, it is visible in all files of the package to which it belongs. The case of the first letter of a name determines its visibility across package boundaries. If the name begins with an upper-case letter, it is exported, which means that it is visible and accessible outside of its own package and may be referred to by other parts of the program, as with Printf in the fmt package. Package names themselves are always in lower case.

There is no limit on name length, but convention and style in Go programs lean toward short names, especially for local variables with small scopes; you are much more likely to see variables named i than theLoopIndex. Generally, the larger the scope of a name, the longer and more meaningful it should be.

Stylistically, Go programmers use “camel case” when forming names by combining words; that is, interior capital letters are preferred over interior underscores. Thus the standard libraries have functions with names like QuoteRuneToASCII and parseRequestLine but never quote_rune_to_ASCII or parse_request_line. The letters of acronyms and initialisms like ASCII and HTML are always rendered in the same case, so a function might be called htmlEscape, HTMLEscape, or escapeHTML, but not escapeHtml.