Regex Problem in Extractor Regular Expression - JMeter - regex

Question

I'm using the regular expression extractor in JMeter to extract data from a parameter.
However, the data is not being extracted.
Response:
{
"access_token": "8d06ba17-2e51-31d2-aa55-25e4a3ecd33b",
"expires_in": 7200
}
Extractor:
Name reference: token
Regular expression: "access_token": "(.+?)"
Match: $1$
Request parameter use
v1/api/users?client=${token}

Answer 1

Use instead JSON Extractor with JSON Path Expressions as $.access_token
JSON PostProcessor enables you extract data from JSON responses using JSON-PATH syntax. This post processor is very similar to Regular expression extractor. It must be placed as a child of HTTP Sampler or any other sampler that has responses. It will allow you to extract in a very easy way text content

Answer 2

Your access_token is a GUID-like structure so you can use the following regular expression instead:
([A-Fa-f0-9]{8}[\-][A-Fa-f0-9]{4}[\-][A-Fa-f0-9]{4}[\-][A-Fa-f0-9]{4}[\-]([A-Fa-f0-9]){12})
Alternatively you can try to secure yourself by adding optional whitespace meta character like:
"access_token"\s?:\s?"(.+?)"
More information:
JMeter: Regular Expressions
Perl 5 Regex Cheat sheet
And finally your response is in JSON format so it makes more sense to use JSON Extractor, the relevant JsonPath query would be as simple as:
$.access_token