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Documentation Index

Fetch the complete documentation index at: https://docs.go-mizu.dev/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

The timezone middleware detects user timezone from headers, cookies, or client hints for proper time display. Use it when you need:
  • Time localization
  • Timezone-aware scheduling
  • User time preferences

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Installation

import "github.com/go-mizu/mizu/middlewares/timezone"

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Quick Start

app := mizu.New()

app.Use(timezone.New())

app.Get("/time", func(c *mizu.Ctx) error {
    tz := timezone.Get(c)
    loc, _ := time.LoadLocation(tz)
    now := time.Now().In(loc)
    return c.JSON(200, map[string]string{
        "timezone": tz,
        "time":     now.Format(time.RFC3339),
    })
})

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Configuration

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Options

OptionTypeDefaultDescription
Defaultstring"UTC"Default timezone
Headerstring"X-Timezone"Timezone header
CookieNamestring"tz"Cookie name

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Examples

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Basic Detection

app.Use(timezone.New())

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Custom Header

app.Use(timezone.New(timezone.Options{
    Header: "X-User-Timezone",
}))

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With Default

app.Use(timezone.New(timezone.Options{
    Default: "America/New_York",
}))

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Client-Side Detection

// Set timezone cookie
document.cookie = `tz=${Intl.DateTimeFormat().resolvedOptions().timeZone}`;

app.Use(timezone.New(timezone.Options{
    CookieName: "tz",
}))

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API Reference

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Functions

// New creates timezone middleware
func New(opts ...Options) mizu.Middleware

// Get returns detected timezone
func Get(c *mizu.Ctx) string

// Location returns time.Location
func Location(c *mizu.Ctx) *time.Location

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Common Timezones

TimezoneDescription
UTCCoordinated Universal Time
America/New_YorkEastern Time
Europe/LondonUK Time
Asia/TokyoJapan Time

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Technical Details

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Implementation

The timezone middleware uses a multi-source detection strategy to identify the user’s timezone:
  1. Context Storage: Timezone information is stored in the request context using a type-safe context key
  2. Info Structure: Contains three key pieces of information:
    • Name: IANA timezone identifier (e.g., “America/New_York”)
    • Location: Parsed time.Location object for time conversions
    • Offset: UTC offset in seconds for the current time
  3. Lookup Order: Configurable detection precedence via the Lookup option (default: “header,cookie,query”)
  4. Validation: Invalid timezone names automatically fall back to the configured default
  5. Cookie Management: Optional automatic cookie setting with configurable max age (default: 30 days)

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Detection Flow

Request → Check Header → Check Cookie → Check Query → Default → Load Location → Store in Context

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Helper Functions

The middleware provides several convenience functions:
  • Get(c): Returns complete timezone info
  • Location(c): Returns time.Location for time operations
  • Name(c): Returns timezone name string
  • Offset(c): Returns UTC offset in seconds
  • Now(c): Returns current time in detected timezone

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Convenience Constructors

  • FromHeader(header): Only check specific header
  • FromCookie(name): Only check specific cookie
  • WithDefault(tz): Set custom default timezone

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Best Practices

  • Default to UTC for storage
  • Convert to user timezone for display
  • Use IANA timezone names
  • Detect via JavaScript for accuracy

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Testing

The middleware includes comprehensive test coverage for all functionality:
Test CaseDescriptionExpected Behavior
TestNewDefault middleware creationReturns UTC timezone when no timezone is detected
TestWithOptions_FromHeaderTimezone detection from headerReads timezone from X-Timezone header (America/New_York)
TestWithOptions_FromCookieTimezone detection from cookieReads timezone from cookie named “timezone” (Europe/London)
TestWithOptions_FromQueryTimezone detection from query parameterReads timezone from “tz” query parameter (Asia/Tokyo)
TestWithOptions_SetCookieCookie setting functionalityAutomatically sets timezone cookie when SetCookie=true
TestWithOptions_InvalidTimezoneInvalid timezone handlingFalls back to UTC default when invalid timezone provided
TestWithOptions_CustomDefaultCustom default timezoneUses America/Los_Angeles as default instead of UTC
TestLocationLocation helper functionReturns correct time.Location object (Europe/Paris)
TestNameName helper functionReturns timezone name string (Australia/Sydney)
TestOffsetOffset helper functionReturns correct UTC offset in seconds (0 for UTC)
TestNowNow helper functionReturns current time in detected timezone location
TestFromHeaderFromHeader constructorCreates middleware that only reads from custom header (X-User-Tz)
TestFromCookieFromCookie constructorCreates middleware that only reads from custom cookie (user_tz)
TestWithDefaultWithDefault constructorCreates middleware with custom default (Asia/Singapore)
TestLookupPrecedenceLookup order precedenceHeader takes precedence over cookie and query when all are present