Set Header

Request Level

Use SetHeader and SetHeaders to set http header at the request level:

// Let's dump the header to see what's going on.
client := req.EnableDumpAllWithoutResponse().EnableForceHTTP1()

// Send a request with multiple headers.
client.R().
    SetHeader("accept", "application/json"). // Set one header
    SetHeaders(map[string]string{            // Set multiple headers at once
        "my-custom-header": "My Custom Value",
        "user":             "imroc",
    }).
    MustGet("https://httpbin.org/uuid")

GET /uuid HTTP/1.1
Host: httpbin.org
User-Agent: req/v3 (https://github.com/imroc/req)
Accept: application/json
My-Custom-Header: My Custom Value
User: imroc
Accept-Encoding: gzip

Use SetHeaderNonCanonical or SetHeadersNonCanonical if you want to keep case unchanged when backend server does not follow the HTTP/1.1 specification “header names are case-insensitive” (see RFC 2616 - 4.2 Message Headers):

// Let's dump the header to see what's going on.
client := req.EnableDumpAllWithoutResponse().EnableForceHTTP1()

client.R().
    SetHeaderNonCanonical("my-Custom-header", "test"). // Set Non-Canonical header in HTTP/1.1, keep case unchanged
    SetHeadersNonCanonical(map[string]string{          // Set multiple non-canonical headers at once
        "my-Custom-Header": "test",
        "my-custom-header": "test",
    }).
    MustGet("https://httpbin.org/uuid")

GET /uuid HTTP/1.1
Host: httpbin.org
User-Agent: req/v3 (https://github.com/imroc/req)
my-Custom-Header: test
my-Custom-header: test
my-custom-header: test
Accept-Encoding: gzip

If you want to control the order of headers to construct HTTP fingerprints, you can use SetHeaderOrder and SetPseudoHeaderOrder:

client.R().SetHeaderOrder(
    "custom-header",
    "cookie",
    "user-agent",
    "accept-encoding",
)

// pseudo-header is only used in http2 and http3
client.R().SetPseudoHeaderOrder(
    ":scheme",
    ":authority",
    ":path",
    ":method",
)

Client Level

Similarly, you can also set the common headers for every request at the client level.

client := req.C()

client.
    SetCommonHeader("accept", "application/json").
    SetCommonHeaders(map[string]string{
        "my-custom-header": "My Custom Value",
        "user":             "imroc",
    }).
    SetCommonHeaderNonCanonical("my-Custom-header", "test").
    SetCommonHeadersNonCanonical(map[string]string{
        "my-Custom-Header": "test",
        "my-custom-header": "test",
    )

resp1, err := client.R().Get(url1)
...
resp2, err := client.R().Get(url2)
...

Control the header order：

client.SetCommonHeaderOrder(
    "custom-header",
    "cookie",
    "user-agent",
    "accept-encoding",
)

// pseudo-header is only used in http2 and http3
client.SetCommonPseudoHeaderOrder(
    ":scheme",
    ":authority",
    ":path",
    ":method",
)
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