fmt.Printf()

General

%v  the value in a default format
  when printing structs, the plus flag (%+v) adds field names
%#v  a Go-syntax representation of the value
%T  a Go-syntax representation of the type of the value  判断类型
%%  a literal percent sign; consumes no value

Boolean:

%t  the word true or false

Integer:

%b  base 2
%c  the character represented by the corresponding Unicode code point
%d  base 10
%o  base 8
%O  base 8 with 0o prefix
%q  a single-quoted character literal safely escaped with Go syntax.
%x  base 16, with lower-case letters for a-f
%X  base 16, with upper-case letters for A-F
%U  Unicode format: U+1234; same as "U+%04X"

Floating-point and complex constituents:

%b  decimalless scientific notation with exponent a power of two,

  in the manner of strconv.FormatFloat with the 'b' format,

  e.g. -123456p-78

%e  scientific notation, e.g. -1.234456e+78

%E  scientific notation, e.g. -1.234456E+78

%f  decimal point but no exponent, e.g. 123.456

%F  synonym for %f

%g  %e for large exponents, %f otherwise. Precision is discussed below.

%G  %E for large exponents, %F otherwise

%x  hexadecimal notation (with decimal power of two exponent), e.g. -0x1.23abcp+20

%X  upper-case hexadecimal notation, e.g. -0X1.23ABCP+20

String and slice of bytes (treated equivalently with these verbs):

%s  the uninterpreted bytes of the string or slice
%q  a double-quoted string safely escaped with Go syntax
%x  base 16, lower-case, two characters per byte
%X  base 16, upper-case, two characters per byte

Slice:

%p  address of 0th element in base 16 notation, with leading 0x

Pointer:

%p  base 16 notation, with leading 0x
The %b, %d, %o, %x and %X verbs also work with pointers,
formatting the value exactly as if it were an integer.

The default format for %v is:

bool:                    %t
int, int8 etc.:          %d
uint, uint8 etc.:        %d, %#x if printed with %#v
float32, complex64, etc: %g
string:                  %s
chan:                    %p
pointer:                 %p

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