How do I find all the constants in a package using go doc?

Question

I've wasted way too much time the past couple of days searching for constants like time.Second and http.StatusOK because they aren't mentioned in go doc time or go doc http respectively.

I specifically searched for a constant representing the duration 1 second by doing:

go doc time | grep Second

With no results, before reading through the entire doc page before concluding that the constant didn't exist. It was only after Googling around for about 15 minutes I happened to see time.Second mentioned somewhere, and when I looked it up directly (go doc time.Second) I found all the duration constants.

How are people supposed to find out about these constants when they're not even mentioned in the official documentation of the package? Am I missing something obvious?

Answer 1

Start with go doc time | grep 'const ':

$ go doc time | grep 'const '
const ANSIC = "Mon Jan _2 15:04:05 2006" ...
const Nanosecond Duration = 1 ...
    const January Month = 1 + iota ...
    const Sunday Weekday = iota ...
$

Then go doc time.Nanosecond:

$ go doc time.Nanosecond
const (
    Nanosecond  Duration = 1
    Microsecond          = 1000 * Nanosecond
    Millisecond          = 1000 * Microsecond
    Second               = 1000 * Millisecond
    Minute               = 60 * Second
    Hour                 = 60 * Minute
)
    Common durations. There is no definition for units of Day or larger to avoid
    confusion across daylight savings time zone transitions.

    To count the number of units in a Duration, divide:

    second := time.Second
    fmt.Print(int64(second/time.Millisecond)) // prints 1000

    To convert an integer number of units to a Duration, multiply:

    seconds := 10
    fmt.Print(time.Duration(seconds)*time.Second) // prints 10s

$ 

---

Start with go doc http | grep 'const ':

$ go doc http | grep 'const '
const MethodGet = "GET" ...
const StatusContinue = 100 ...
const DefaultMaxHeaderBytes = 1 << 20
const DefaultMaxIdleConnsPerHost = 2
const TimeFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
const TrailerPrefix = "Trailer:"
    const StateNew ConnState = iota ...
$

Then go doc http.StatusContinue:

$ go doc http.StatusContinue

package http // import "net/http"

const (
    StatusContinue           = 100 // RFC 7231, 6.2.1
    StatusSwitchingProtocols = 101 // RFC 7231, 6.2.2
    StatusProcessing         = 102 // RFC 2518, 10.1

    StatusOK                   = 200 // RFC 7231, 6.3.1
    StatusCreated              = 201 // RFC 7231, 6.3.2
    StatusAccepted             = 202 // RFC 7231, 6.3.3
    StatusNonAuthoritativeInfo = 203 // RFC 7231, 6.3.4
    StatusNoContent            = 204 // RFC 7231, 6.3.5
    StatusResetContent         = 205 // RFC 7231, 6.3.6
    StatusPartialContent       = 206 // RFC 7233, 4.1
    StatusMultiStatus          = 207 // RFC 4918, 11.1
    StatusAlreadyReported      = 208 // RFC 5842, 7.1
    StatusIMUsed               = 226 // RFC 3229, 10.4.1

    StatusMultipleChoices  = 300 // RFC 7231, 6.4.1
    StatusMovedPermanently = 301 // RFC 7231, 6.4.2
    StatusFound            = 302 // RFC 7231, 6.4.3
    StatusSeeOther         = 303 // RFC 7231, 6.4.4
    StatusNotModified      = 304 // RFC 7232, 4.1
    StatusUseProxy         = 305 // RFC 7231, 6.4.5

    StatusTemporaryRedirect = 307 // RFC 7231, 6.4.7
    StatusPermanentRedirect = 308 // RFC 7538, 3

    StatusBadRequest                   = 400 // RFC 7231, 6.5.1
    StatusUnauthorized                 = 401 // RFC 7235, 3.1
    StatusPaymentRequired              = 402 // RFC 7231, 6.5.2
    StatusForbidden                    = 403 // RFC 7231, 6.5.3
    StatusNotFound                     = 404 // RFC 7231, 6.5.4
    StatusMethodNotAllowed             = 405 // RFC 7231, 6.5.5
    StatusNotAcceptable                = 406 // RFC 7231, 6.5.6
    StatusProxyAuthRequired            = 407 // RFC 7235, 3.2
    StatusRequestTimeout               = 408 // RFC 7231, 6.5.7
    StatusConflict                     = 409 // RFC 7231, 6.5.8
    StatusGone                         = 410 // RFC 7231, 6.5.9
    StatusLengthRequired               = 411 // RFC 7231, 6.5.10
    StatusPreconditionFailed           = 412 // RFC 7232, 4.2
    StatusRequestEntityTooLarge        = 413 // RFC 7231, 6.5.11
    StatusRequestURITooLong            = 414 // RFC 7231, 6.5.12
    StatusUnsupportedMediaType         = 415 // RFC 7231, 6.5.13
    StatusRequestedRangeNotSatisfiable = 416 // RFC 7233, 4.4
    StatusExpectationFailed            = 417 // RFC 7231, 6.5.14
    StatusTeapot                       = 418 // RFC 7168, 2.3.3
    StatusMisdirectedRequest           = 421 // RFC 7540, 9.1.2
    StatusUnprocessableEntity          = 422 // RFC 4918, 11.2
    StatusLocked                       = 423 // RFC 4918, 11.3
    StatusFailedDependency             = 424 // RFC 4918, 11.4
    StatusUpgradeRequired              = 426 // RFC 7231, 6.5.15
    StatusPreconditionRequired         = 428 // RFC 6585, 3
    StatusTooManyRequests              = 429 // RFC 6585, 4
    StatusRequestHeaderFieldsTooLarge  = 431 // RFC 6585, 5
    StatusUnavailableForLegalReasons   = 451 // RFC 7725, 3

    StatusInternalServerError           = 500 // RFC 7231, 6.6.1
    StatusNotImplemented                = 501 // RFC 7231, 6.6.2
    StatusBadGateway                    = 502 // RFC 7231, 6.6.3
    StatusServiceUnavailable            = 503 // RFC 7231, 6.6.4
    StatusGatewayTimeout                = 504 // RFC 7231, 6.6.5
    StatusHTTPVersionNotSupported       = 505 // RFC 7231, 6.6.6
    StatusVariantAlsoNegotiates         = 506 // RFC 2295, 8.1
    StatusInsufficientStorage           = 507 // RFC 4918, 11.5
    StatusLoopDetected                  = 508 // RFC 5842, 7.2
    StatusNotExtended                   = 510 // RFC 2774, 7
    StatusNetworkAuthenticationRequired = 511 // RFC 6585, 6
)
    HTTP status codes as registered with IANA. See:
    https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
$ 

Answer 2

Sorry, took me some time to realize it. Actually, we're looking at a wrong command line tool. Use godoc time instead.

If you don't have it, you can install it as follows:

$ go get golang.org/x/tools/cmd/godoc
$ go build golang.org/x/tools/cmd/godoc

Then copy it to your path (or run from where it is).