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package middleware
import (
"strings"
"github.com/labstack/echo/v4"
)
func mergeHeaders(c echo.Context) {
hdr := c.Response().Header()
// echo duplicates the Vary header a few places so deduplicate them and
// write it out as a comma separated list instead of as many duplicate
// headers.
if vh := hdr.Values(echo.HeaderVary); len(vh) > 1 {
seen := map[string]bool{}
out := []string{}
for _, v := range vh {
if _, ok := seen[v]; !ok {
seen[v] = true
out = append(out, v)
}
}
hdr.Set(echo.HeaderVary, strings.Join(out, ", "))
}
}
// MergeHeaders merges together specific sets of duplicated headers. It
// doesn't try to be a general solution to header duplication because
// that would be too error prone. Currently this only works for the Vary
// header.
func MergeHeaders() echo.MiddlewareFunc {
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
c.Response().Before(func() { mergeHeaders(c) })
return next(c)
}
}
}
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