using telegraf with plugin http , Error x509: certificate signed by unknown authority

Question

I Use Telegraf with http plugin

[[outputs.http]]
url = "https://example.com/test/rest/login"
method = "POST"
tls_ca = "/etc/telegraf/ssl1/cert.pem"
tls_cert = "/etc/telegraf/ssl1/cert.pem"
tls_key = "/etc/telegraf/ssl1/key.pem"

but I get an error

Error writing to outputs.http: Post "https://example.com/test/rest/login": x509: certificate signed by unknown authority

I call with the same information with CURL Command and the command works correctly

curl -v -H "Content-Type: application/json" --key /etc/telegraf/ssl1/key.pem --cert /etc/telegraf/ssl1/cert.pem -d'{"username":"username","password":"password"}' https://example.com/test/rest/login

Also, I call the folowing command for the correctness of the certificate

openssl s_client -connect example.com:443 -CApath /etc/ssl/certs

CONNECTED Verification: OK Verify return code: 0 (ok)

please help me how to solve my problem in telegraf