redis setstring System.NullReferenceException: 'Object reference not set to an instance of an object.'

Question

I want to set cache to redis but I get an reror:

System.NullReferenceException: Object reference not set to an instance of an object.

My code

DistributedCacheEntryOptions options = new DistributedCacheEntryOptions();
options.AbsoluteExpiration = DateTime.Now.AddMinutes(1);
options.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(1);
options.SlidingExpiration = TimeSpan.FromSeconds(30);

_distributedCache.SetString("zaman", DateTime.Now.ToString(), options);

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Even though I filled in all the relevant fields, the code throws a System.NullReferenceException