snmpwalk "Timeout no response" means exactly that - no response was obtained from the device. The "context canceled" means pretty much the same.
Therefore, you need to debug first why snmpwalk or snmpstatus doesn't work, before configuring snmp_exporter.
Some possible reasons:
* the device is not network reachable from where you are running snmpwalk (try pinging x.x.x.x)
* snmp agent is not enabled on the device
* the device is not configured for SNMP v2c
* an ACL on the device does not allow SNMP queries from your address
* you are using the wrong community string (i.e. it's not "public", or none has been configured)